University  of  California— College  of  Agriculture, 

AGRICULTURAL  EXPERIMENT  STATION. 
E.  W.  HILGARD,  Director. 


PARIS  GREEN  FOR  THE  CODLING-MOTH. 

By  C.  W.  Woodworth  and  Geo.  E.  Colby. 

Pure. 


Paris  Green,  as  It  Appears  Under  the  Microscope. 

BULLETIN  No.  126. 


SACRAMENTO: 

A.  J.  Johnston,      :      :      Superintendent  of  State  Printing. 

1899. 


SUMMARY  OF  CONTENTS. 

With  Page  References. 


Paris  green  as  now  found  on  the  market  is  often  unsatisfactory  (p.  3),  occa- 
sionally a  bogus  article  (p.  8),  sometimes  adulterated  (p.  8),  commonly  low 
grade  (p.  9),  and  very  often  with  much  free  arsenic  (p.  9),  which  is  danger- 
ous to  foliage  (p.  9),  especially  in  California  (p.  10),  and  the  injury  from 
which  cannot  always  be  prevented  by  the  addition  of  lime  (p.  11). 

Pure  Paris  green  will  dissolve  wholly  in  ammonia  (p.  12) ;  it  will  make  a 
green  streak  on  glass  (p.  12),  and  consists  of  green  spheres,  as  seen  under  the 
microscope  (p.  13) ;  the  latter  is  the  best  test,  but  chemical  analysis  is  neces- 
sary to  determine  the  grade,  and  the  presence  of  soluble  white  arsenic  or 
arsenites  (p.  14).  Freedom  from  soluble  arsenical  compounds  and  a  known 
grade  are  essential  in  a  spraying  material  (p.  14).  Laws  have  so  far  failed  to 
recognize  this  (p.  15),  and  better  standards  are  essential  (p.  16).  The  Uni- 
versity of  California  will  condemn  all  samples  of  Paris  green  that  are  not 
pure  (as  shown  by  the  microscope),  or  if  they  contain  water-soluble  arsenical 
compounds,  or  if  they  fall  below  fifty  per  cent  of  arsenious  oxid  (p.  17). 

Under  the  present  circumstances  the  use  of  substitutes  for  Paris  green  is 
recommended  (p.  17).  These  can  be  obtained  ready-made,  in  considerable 
variety,  but  there  is  no  assurance  that  their  quality  will  be  maintained 
(p.  18).  Home-made  articles  are  the  cheapest,  are  easily  made,  and  have 
been  quite  thoroughly  tested  (p.  22),  but  they  require  more  care  in  handling 
because  of  the  danger  of  poisoning  (p.  24). 

Other  remedies  for  the  codling-moth  have  been  tried,  and,  under  some 
circumstances,  might  be  used  to  supplement  spraying  (p.  25),  such  as  the  use 
of  bands  (p.  25),  destruction  of  "windfalls"  (p.  26),  destruction  of  moths  in 
fruit-houses  (p.  26),  and  traps  (p.  27);  while  others,  like  winter  spraying,  are 
useless  (p.  27).  Mistakes,  often  made,  which  should  be  avoided  are  as  fol- 
lows: Too  few  applications  (p.  28),  lack  of  uniformity  (p.  28),  and  failure  to 
appreciate  difference  of  location  (p.  29)  and  season  (p.  30).  The  codling-moth 
can  be  fought  effectively  (p.  30) ;  the  correct  practice  is  that  which  brings 
the  best  return  for  time  and  money  invested  in  treatment  (p.  31).  This  will 
vary  with  locality  and  season,  and  therefore  requires  intelligent  considera- 
tion of  conditions  (p.  31) ;  and  finally  the  spraying  must  be  thoroughly  and 
carefully  done  (p.  32). 

Arsenious  oxid  soluble  in  water  occurs  in  many  samples  of  Paris  green 
(p.  33);  Paris  green,  if  pure,  though  a  variable  compound,  should  be  wholly 
insoluble  (p.  34).  The  commercial  article  should  not  contain  much  over  four 
per  cent  (p.  34).  Objectionable  samples  showed  on  analysis  from  seven  to 
thirty  per  cent  of  free  oxid  (p.  35).  No  really  adulterated  samples  have  been 
analyzed  (p.  37).  Some  of  the  newer  Paris  green  substitutes  were  examined 
(p.  37),  including  White  arsenoid  (p.  38),  Pink  arsenoid  (p.  38),  Green  arsenoid 
(p.  38),  and  Paragrene  (p.  39).    The  results  are  summarized  on  the  last  page. 


PARIS  GREEN  FOR  THE  CODLING-MOTH. 


By  C.  W.  Woodworth. 


Paris  green  is  practically  the  only  substance  that  has  been 
widely  and  extensively  used  as  a  remedy  for  the  codling-moth. 
During  the  last  three  or  four  years  a  great  deal  of  complaint 
has  been  made,  both  here  and  in  the  Eastern  States,  because  of 
the  failure  to  obtain  the  same  good  results  as  formerly,  even  by 
orchardists  who  do  very  careful  work  and  have  previously  had 
the  best  of  results.  During  this  same  period  there  has  been  a 
decided  change  in  the  microscopic  appearance  of  most  of  the 
Paris  green  on  the  market,  indicating  a  large  amount  of  adul- 
teration on  the  one  hand  and  a  different  and  less  satisfactory 
method  of  manufacture  on  the  other.  The  situation  became 
so  thoroughly  unendurable  that  this  Station  sent  out  the  fol- 
lowing circular  letter  to  the  entomologists  of  the  various 
experiment  stations,  and  to  the  editors  of  a  number  of  agricul- 
tural newspapers,  in  order  to  obtain  the  opinions  of  these 
parties  and  the  facts  in  their  possession: 

University  of  California,  Agricultural  Experiment  Station. 

College  of  Agriculture,  E.  W.  Hilgard,  Director. 

Berkeley,  Calif. 

Dear  Sir  :  This  Station  has  given  considerable  attention  to  the  matter  of 
the  adulteration  of  Paris  green,  and  we  are  convinced  that  at  the  present 
time  there  is  scarcely  any  strictly  pure  Paris  green  on  the  market,  whether 
here  or  in  the  Eastern  States. 

It  appears  to  me  that  it  will  be  necessary  for  experiment  stations  and 
agricultural  newspapers  to  cease  to  recommend  Paris  green  as  an  insecticide 
the  coming  season,  and  substitute  home-made  arsenites. 

I  write  this  note  to  request  that  you  send  me  what  information  you  may 
have  upon  arsenite  of  lime  and  arsenite  of  lead,  especially  as  to  their  effect- 
iveness against  codling-moth. 

This  information  I  propose  to  compile  and  publish,  giving  due  credit,  and 
hope  I  shall  secure  your  hearty  cooperation. 

Yours  truly,  C.  W.  WOODWORTH. 


—  4  — 

Replies  to  this  circular  were  received  from  the  following 
persons,  to  whom  acknowledgments  are  due: 

E.  F.  Adams,  agricultural  editor  Weekly  Chronicle,  San 
Francisco,  California;  Prof.  J.  M.  Aldrich,  Moscow,  Idaho; 
Prof.  E.  E.  Bogue,  Stillwater,  Oklahoma;  Prof.  H.  A.  Bolley, 
Agricultural  College,  North  Dakota;  Prof.  W.  E.  Britton,  New 
Haven,  Connecticut;  Prof.  Lawrence  Brunner,  Lincoln,  Ne- 
braska; Prof.  B.  C.  Buffum,  Laramie,  Wyoming;  Prof.  Geo.  C. 
Butz,  State  College,  Pennsylvania;  Prof.  Fred  W.  Card, 
Kingston,  Rhode  Island;  E.  P.  Claebe,  editor  Press  and  Horti- 
culturist, Riverside,  California;  Prof.  J.  H.  Comstock,  Ithaca, 
New  York;  Prof.  A.  B.  Cordley,  Corvallis,  Oregon;  Prof.  F.  S. 
Earle,  Auburn,  Alabama;  Director  E.  H.  Forbush,  Gypsy- 
Moth  Committee,  Maiden,  Massachusetts;  Prof.  H.  Garman, 
Lexington,  Kentucky;  Prof.  C.  P.  Gillette,  Fort  Collins,  Colo- 
rado; Prof.  E.  S.  GofF,  Madison,  Wisconsin;  Prof.  H.  A.  Gos- 
sard,  Lake  City,  Florida;  Prof.  H.  H.  Harrington,  College 
Station,  Texas;  Prof.  F.  L.  Harvey,  Orono,  Maine;  Prof.  U.  P. 
Hedrick,  Logan,  Utah;  Prof.  Glen  W.  Herrick,  Agricultural 
College,  Mississippi;  Editor  Iowa  Homestead,  Des  Moines, 
Iowa;  Prof.  W.  G.  Johnson,  College  Park,  Maryland;  Prof.  K. 
C.  Kedzie,  Agricultural  College,  Michigan;  Prof.  U.  H.  Lowe, 
Geneva,  New  York;  Prof.  H.  A.  Morgan,  Baton  Rouge,  Louisi- 
ana; A.  N.  Pearsall,  editor  American  Horticulturist,  Monroe, 
Michigan;  Prof.  A.  L.  Quaintance,  Experiment  Station,  Georgia; 
Prof.  P.  H.  Rolfs,  Clemson  College,  South  Carolina;  B.  N.  Rowley, 
editor  California  Fruit-Grower,  San  Francisco,  California;  Prof. 
Geo.  W.  Shaw, Corvallis,  Oregon ;  Prof.  M.  V.  Slingerland,  Ithaca, 
New  York;  Hon.  E.  L.  Smith.  Hood  River,  Oregon;  Prof.  J.  B. 
Smith,  New  Brunswick,  New  Jersey;  H.  P.  Stabler,  Yuba  City, 
California;  Prof.  J.  N.  Stedman,  Columbia,  Missouri;  Prof. 
Wm.  C.  Stubbs,  New  Orleans,  Louisiana;  Prof.  H.  E.  Summers, 
Ames,  Iowa;  Prof.  L.  R.  Taft,  Agricultural  College,  Michigan; 
Prof.  James  Troop,  Lafayette,  Indiana;  Prof.  E.  B.  Voorhees, 
New  Brunswick,  New  Jersey;  Prof.  Ernest  Walker,  Clemson 
College,  South  Carolina;  Prof.  F.  N.  Webster,  Wooster,  Ohio; 
H.  N.  Williamson,  editor  Oregon  Agriculturalist  and  Rural 
Northwestern,  Portland,  Oregon. 


-  5  — 
Purity  of  Paris  Green. 

There  is  by  no  means  unanimity  of  opinion  as  to  the  char- 
acter of  the  Paris  green  usually  found  on  the  market,  as  can  be 
seen  by  the  following  extracts  of  letters  received: 

Professor  Slingerland,  of  Cornell  University,  writes:  "I  can 
hardly  agree  with  your  first  premises  that  there  is  scarcely  any 
strictly  pure  Paris  green  on  the  market;  at  least,  not  in  the  State 
of  New  York,  for  here  we  have  a  law  requiring  Paris  green  and 
similar  poisonous  insecticides  to  contain  at  least  fifty  per  cent 
of  arsenic.  Many  samples  of  Paris  green  have  been  analyzed 
by  our  chemist  here,  and  but  very  few  of  them  are  below  this 
standard.  We  receive  but  very  little  complaint  which  would 
indicate  that  Paris  green  was  impure."  Again,  from  South 
Carolina  Professor  Rolfs  writes:  "I  have  used  Paris  green 
with  good  effect  for  a  number  of  years,  and  have  found  it  effect- 
ive this  year."  Professor  Walker  says:  "  It  is  probably  less 
(adulterated)  now  than  formerly,"  and  cites  considerable 
number  of  analyses  made  by  that  station  showing  the  total 
arsenic  to  be  above  fifty-five  per  cent.  Professor  Harrington,  of 
the  University  of  Texas,  writes:  aThis  is  the  first  year  we  have 
had  a  law  in  this  State  controlling  the  sale  of  Paris  green  and 
poisonous  insecticides.  We  have  analyzed  a  number  of  sam- 
ples this  year  and  found  most  of  them  pure.  They  were  mostly 
from  New  York  manufacturers."  Professor  Garman,  of  Ken- 
tucky, writes:  "The  samples  of  Paris  green  analyzed  here,  in 
some  cases  proved  to  be  imitations,  but  most  of  those  we  have 
used  contained  fifty  per  cent  and  upward  of  arsenic — evidence 
that  they  had  not  been  tampered  with.  However,  I  have  not 
given  special  attention  to  the  adulteration  of  insecticides,  and 
it  may  prove  that  Paris  green  commonly  sold  from  groceries 
and  drug  stores  is  more  often  adulterated  than  our  experience 
would  indicate.  The  Paris  green  used  by  me  has  been  obtained 
mostly  from  well-known  and  reliable  dealers  in  insecticides." 
Professor  Taft,  of  Michigan  Agricultural  College,  writes:  "My 
experience  with  Paris  green  has  not  resembled  yours,  so  far  as 
finding  it  adulterated  is  concerned."  Professor  Gillette,  of 
Colorado,  writes:  "The  few  tests  that  we  have  made  here  of 
Paris  green  indicate  that  this  poison  is  fairly  pure."  Finally, 
Professor  Cordley,  of  Corvallis,  Or.,  says:  "Last  year  our 
chemist,  Professor  Shaw,  made  something  of  a  study  of  the 
2ub 


—  6  — 

Paris  green  sold  in  the  State,  and  reported  it  as  reasonably 
pure." 

Professor  Smith,  of  the  New  Jersey  station,  writes:  "We 
have  not  found  any  willful  adulterations.  We  have  found  very 
great  variation  in  arsenic  contents." 

The  evidence  on  the  other  hand,  showing  the  adulteration  of 
Paris  green,  seems  quite  as  extensive. 

Professor  Johnson,  of  Maryland,  writes:  "Have  had  much 
trouble  with  l bogus'  Paris  green."  Professor  Quaintance,  of 
Georgia,  writes:  "I  heartily  agree  with  you  in  your  sentiments 
concerning  this  article,  and  am  convinced  that  Paris  green  is 
being  greatly  adulterated.  This  seems  particularly  probable 
from  the  uncertain  results  which,  from  my  own  experience,  I 
have  had  to  follow  from  the  use  of  this  arsenite."  Professor 
Troop,  of  Indiana,  says:  "I  have  been  of  the  opinion  for  some 
time  ihat  the  Paris  green  on  our  markets  was  not  the  pure 
article,  because  of  the  numerous  letters  that  I  have  received 
complaining  that  it  did  not  do  the  work."  Professor  Webster, 
of  Ohio,  says:  "I  certainly  believe  that  what  you  say  is  correct, 
for  I  can  seldom  get  the  same  results  where  it  is  recommended 
for  a  particular  purpose  to  a  considerable  number  of  corre- 
spondents. Frequently,  I  find  that  in  the  hands  of  one  per- 
son the  Paris  green  is  effective,  while  another  one  using  it 
equally  carefully,  has  failed  entirely.  Of  course,  I  have  but 
one  way  of  accounting  for  this  difficulty."  Mr.  Pearsall,  of 
Monroe,  Mich.,  writes:  "There  is  no  doubt  that  the  adultera- 
tion of  Paris  green  has  grown  to  such  an  extent  that  in  many 
cases  the  effects  of  its  use  are  practically  nil,  and  some  substi- 
tute must  be  found."  Professor  Steadman,  of  the  University  of 
Missouri,  writes:  "It  is  very  difficult  for  horticulturists  and 
farmers  of  this  State  to  get  really  pure  Paris  green,  or  London 
purple;  almost  impossible  if  they  procure  it  at  their  little 
country  towns.  I  have  seen  samples  of  Paris  green  that  con- 
tained no  poison  of  any  kind.  It  was  plaster  of  paris  colored 
with  indigo  and  chrome  yellow."  Professor  Brunner,  of 
Nebraska,  remarks:  rt  We  have  also  had  considerable  trouble  of 
recent  years  in  finding  our  experiments  to  be  very  uncertain 
and  irregular.  Our  correspondents  have,  also,  from  time  to 
time  said  that  the  results  obtained  by  using  this  poison  for  the 
destruction  of  insects  have  been  uncertain.  They  also  ascribe 
the  difficulty  to  impure  poison." 


—  7  — 

In  California  the  opinions  of  fruit-growers  are  almost  unani 
mous  in   regard  to  the  unreliability  of   Paris  green,  as  they 
obtain  the  best  results  at  times,  and  at  other  times  very  poor. 
A  few  quotations  will  be  sufficient  to  indicate  this: 

E.  P.  Claebe,  of  Riverside,  writes:  "I  referred  the  circular 
to  the  president  of  our  Horticultural  Club,  who  reports  that 
the  experience  of  horticulturists  regarding  Paris  green  has 
been  very  unsatisfactory."  H.  P.  Stabler,  of  Yuba  City, 
writes:  "We  are  ready  to  agree  with  you  that  the  goods  are 
generally  adulterated."  B.  N.  Rowley,  of  San  Francisco, 
writes:  "I  have  been  aware  for  some  considerable  time  that 
growers  were  spending  money  and  wasting  their  time  spraying 
trees  with  what  they  thought  was  Paris  green,  in  which  there 
was  not  enough  poison  in  a  gallon  to  kill  a  single  codling-moth, 
but  so  long  as  the  people  want  things  cheap  and  keep  crowd- 
ing down  the  price,  manufacturers  are  bound  to  supply  the 
demand,  and  adulterations  follow.  If  fruit-growers  are  willing 
to  pay  the  price  they  could  be  supplied  with  pure  Paris  green, 
or  as  nearly  pure  as  factories  can  produce  it.  This  would 
compel  buyers  in  small  quantities  to  pay  possibly  twenty- 
seven  or  thirty  cents  a  pound.  They  prefer  to  buy  chalk  and 
salt  and  various  other  substances  at  ten  and  twelve  cents  a 
pound,  wasting  both  time  and  money." 

These  differences  of  opinion  are  explainable  in  a  number  of 
ways:  they  may  be  due,  in  part,  to  the  fact  that  in  some  cases 
the  samples  of  Paris  green  obtained  and  analyzed  by  station 
workers  were  from  firms  of  known  integrity;  in  part,  to  the 
fact  that  in  some  cases  they  were  obtained  after  laws  had  been 
enacted  requiring  a  certain  standard  of  excellence;  and  in  a 
measure,  also,  because  this  standard  (the  presence  of  fifty  per 
cent  of  arsenic)  is  one  very  easily  obtained,  even  in  badly 
adulterated  samples,  providing  part  of  the  adulterant  be 
arsenious  oxid.  On  the  other  hand  it  is  undoubtedly  true  that 
complaint  is  often  made  of  the  quality  of  the  poison,  when  the 
whole  fault  lies  with  the  user. 

A  considerable  number  of  samples  made  and  sold  in  New 
York  under  the  names  of  leading  makers  have  been  recently 
examined  and  condemned  by  us,  mostly  on  microscopic  evi- 
dence, though  subsequently  confirmed  chemically.  They  prove 
that  the  situation  in  the  Eastern  States  is  no  better  than  in 


—  8  — 

California.     A  large   jobber  writes  that   none   better   can  be 
found  on  the  market  than  these  condemned  samples. 

It  is  not  contended  that  there  is  wholesale  willful  adulteration 
of  Paris  green,  nor  that  a  large  proportion  of  the  material  sold 
will  not  come  up  to  the  legal  requirement  of  the  States  which 
attempt  to  control  its  purity.  The  fact  is  nevertheless  easily- 
demonstrated  that  but  little  of  the  Paris  green  on  the  market  is 
really  a  satisfactory  article  for  spraying  purposes. 

Forms  of  Impurities. 

Three  distinct  classes  of  unsatisfactory  Paris  green  can  be 
recognized,  which  we  would  designate,  respectively,  as  bogus, 
adulterated,  and  low-grade  Paris  green. 

Bogus  Paris  Green. — Under  this  title  is  included  that 
series  of  out-and-out  imitations  of  Paris  green  in  which  the 
color  is  produced  from  other  substances  than  copper,  and  which 
usually  contain  no  trace  either  of  copper  or  of  arsenic.  They 
are  usually  perfectly  harmless  to  the  plant  and  to  the  insect, 
and  quite  decidedly  cheaper  than  Paris  green.  They  are  sold 
mostly  by  paint  dealers,  and  were  probably  manufactured  for 
use  as  a  cheaper  form  of  green  pigment  than  is  Paris  green. 

We  have  very  little  information  of  their  extensive  sale  in 
California  as  Paris  green,  though  both  Mr.  Rowley,  of  the 
"  Fruit  Grower,"  and  Secretary  B.  M.  Lelong,  of  the  State 
Board  of  Horticulture,  have  met  with  samples  sold  as  bona 
fide  Paris  green.  It  is  probable  that  none  of  these  articles 
would  stand  the  ammonia  test  described  below ;  certainly, 
they  would  be  at  once  recognized  under  the  microscope. 

Adulterated  Paris  Green. — This  class  of  Paris  green  is 
often  sold  by  unscrupulous  dealers — sometimes  by  honest 
dealers  who  have  been  supplied  by  unscrupulous  jobbers — and 
indicates  always  an  intention  of  fraud  on  the  part  of  some  one. 
They  consist  of  Paris  green  in  part,  generally  upward  of  fifty 
per  cent,  and  to  this  is  added  some  other  substance  for  the 
purpose  of  increasing  the  weight.  Any  white  powder,  such  as 
gypsum,  will  do,  and  even  flour  has  been  used.  The  intensity 
of  the  green  color  in  good  Paris  green  allows  considerable 
addition  of  white  material,  though  in  some  cases  green  or  blue 
pigments  are  added  to  prevent  detection.     Most  of  these  forms 


—  9  — 

of  cheapening  Paris  green  are  at  once  recognized  in  all  three  of 
the  tests  given  below,  and  especially  are  they  at  once  detected 
under  the  microscope. 

Low-Grade  Paris  Green. — The  third  type  of  unsatisfactory 
Paris  green,  and  the  one  most  difficult  to  recognize,  is  a  "low- 
grade  Paris  green";  by  which  term  it  is  intended  to  designate 
those  manufactured  in  such  a  way  as  to  contain  a  low  per  cent 
of  arsenious  oxid  in  combination.  A  strictly  pure  Paris  green 
can  be  produced,  according  to  our  observations,  with  not  over 
forty  per  cent  of  arsenious  oxid,  but  such  a  sample  is  simply 
low-grade.  To  use  such  in  spraying  would  require  nearly  one- 
half  more  material  to  produce  effective  spraying,  than  would 
be  necessary  with  a  sample  containing  the  normal  fifty-eight 
per  cent  of  arsenious  oxid.  For  this  class  of  green  it  appears 
that  the  only  test  now  available  is  the  chemical  determination 
of  the  quantity  of  arsenic  present. 

The  production  of  low-grade  Paris  green  is  almost  as  expen- 
sive, or  perhaps  quite  as  expensive,  so  far  as  the  ingredients 
used  are  concerned,  as  is  the  production  of  the  high-grade 
article. 

It  therefore  appears  that  the  low-grade  greens  are  produced 
not  with  any  intention  of  defrauding  the  public,  but  rather 
because  of  the  ease  of  manufacture.  The  laws,  especially  of 
New  York  where  the  greatest  amount  of  Paris  green  is  manu- 
factured, require  the  total  arsenious  oxid  to  be  above  fifty  per 
cent,  and  this  has  required  the  addition,  either  during  or  after 
manufacture,  of  sufficient  arsenious  oxid  in  the  free  state  to 
come  within  the  requirements  of  the  law.  As  a  result  of  this 
the  greater  part  of  the  low-grade  Paris  green  on  the  market 
contains  as  an  adulterant  a  considerable  proportion  of  the  free 
acid.  The  determinations  that  have  been  heretofore  made 
have  only  taken  into  consideration  the  total  arsenic  per  cent, 
and  so  all  these  samples  of  low-grade,  "doctored"  Paris  green 
have  been  passed  as  pure. 

Danger  from  Arsenical  Adulterations. 

White  arsenic  (arsenious  oxid),  as  has  long  been  known,  is 
very  injurious  to  foliage;  for  this  reason,  it  is  scarcely  at  all 
used  for  the  destruction  of  insects.  It  is  much  cheaper  than 
Paris  green,  and  were  it  not   for  the  injury  to  foliage  would 


—  10  — 

have  been  used  entirely  instead  of  Paris  green.  The  one  thing 
which  has  made  the  latter  the  standard  insecticide  has  been  its 
insolubility.  Of  late  years,  since  the  addition  of  free  white 
arsenic  has  become  a  common  practice  by  the  manufacturers, 
or  by  adulterators,  the  unreliability  of  Paris  green  in  its  influ- 
ence on  foliage  has  been  repeatedly  noticed.  In  the  hands  of 
the  farmer  this  is  almost  sure  to  result  in  a  diminution  of  the 
dose  until  the  injury  becomes  unimportant.  On  the  farm  it  is 
the  practice  to  weigh  and  measure  things  very  carelessly,  and 
the  difference  between  full  measure  and  scant  measure,  even 
when  the  farmer  thinks  he  is  following  directions,  amounts  to  a 
very  great  deal.  The  diminution  of  dose  has  been  one  of  the 
causes,  and  an  important  one,  of  the  complaint  of  the  inef- 
fectiveness of  Paris  green,  which  we  have  heard  from  all  over 
the  United  States,  during  the  last  few  years. 

The  danger  to  foliage  from  free  arsenic  has  also  resulted  in 
the  change  of  the  formula  now  usually  recommended,  by 
attempting  to  neutralize  the  soluble  substances  in  the  Paris 
green  by  the  addition  of  lime.  This  matter  will  be  referred  to 
again  below  and  in  more  detail.  The  addition  of  lime  has  been 
more  or  less  successful  when  the  amount  of  arsenic  was  not  too 
large,  but  one  of  the  great  advantages  of  Paris  green — that 
which  more  than  anything  else  has  caused  it  to  hold  its  own  as 
an  insecticide — is  the  fact  that  no  preparation  is  necessary. 
The  substance  as  it  is  purchased  from  the  store  is  stirred  up  in 
water  and  is  at  once  ready  for  use.  If  it  is  necessary  to  add 
some  material  to  neutralize  the  free  arsenious  oxid,  it  will  be 
better  to  take  slightly  more  trouble  and  decrease  the  cost  of  the 
material  by  the  use  of  home-made  arsenites. 

Causes  of  Injury  to  Foliage. 

While  Paris  green  is  entirely  insoluble  in  pure  water,  it 
appears  that  as  ordinarily  used  a  certain  amount  of  it  does 
find  its  way  into  solution  and  thus  enters  the  plant;  and  if 
very  much  goes  in,  the  death  of  the  part  of  the  plant  thus 
poisoned  ensues.  The  most  critical  period  seems  to  be  the 
time  during  which  the  spray  remains  wet  upon  the  leaf,  and 
each  subsequent  wetting  of  the  leaf  from  any  cause,  such  as  a 
fog  or  dew,  continues  the  danger.  It  has  been  demonstrated 
repeatedly  that  dry  Paris  green  can  be  placed  upon  a  leaf  in 


—  11  — 

any  quantity,  and  so  long  as  the  leaf  remains  dry  no  evil 
results  will  follow.  After  an  application  in  the  wet  way, 
almost  immediately,  within  twenty-four  hours,  a  blackening  of 
the  leaf  or  of  parts  of  the  leaf  may  occur,  or  the  leaf  may 
entirely  escape  at  that  time,  but  later,  after  a  dew  or  fog,  show 
the  signs  of  the  action  of  the  poison;  or  again,  there  may  be  no 
blackening  of  the  leaf  observed  at  any  time,  but  the  leaf  may 
become  prematurely  yellow  and  drop  off  within  two  or  three 
weeks  from  the  time  the  application  was  made;  showing  that 
the  poison  which  entered  the  plant,  though  not  enough  to 
kill  it  at  once,  deranged  its  functions  to  such  an  extent  as  to 
cause  this  premature  dropping.  These  two  forms  of  poisoning 
we  have  designated  as  the  acute  and  the  chronic  poisoning  of 
arsenic. 

The  amount  of  poisoning  that  may  occur,  other  things  being 
equal,  seems  to  be  entirely  dependent  upon  the  amount  of 
soluble  arsenic  in  the  spraying  mixture,  though  there  are  con- 
ditions of  the  plant  when  it  is  possible  to  spray  even  with  a 
solution  of  arsenic  and  produce  no  evil  effects.  We  know  that 
under  certain  conditions  leaves  will  absorb  water,  and  under 
other  conditions  not  at  all;  so  it  may  be  supposed  in 
cases  where  solutions  of  arsenic  have  been  applied  without 
injury,  that  the  plant  was  in  such  a  condition  that  no  absorp- 
tion of  water  took  place  and  none  of  the  arsenic  solution  entered 
the  plant;  and  that  before  the  leaves  became  again  absorbent 
the  water  had  evaporated,  leaving  the  arsenic  upon  the  leaves 
in  a  dry  form.  This  might  flake  off  and  blow  away  from  the 
leaves  before  they  are  exposed  to  a  dew  or  fog.  It  may  be  that 
when  we  know  more  about  the  effect  of  weather  upon  the 
leaves,  we  will  be  able  to  spray  at  times  when  the  leaf  is  least 
susceptible  to  injury,  and  so  lessen  the  danger  to  the  plant. 

Prevention  of  Injury. — A  chemical  means  of  avoiding  the 
injury  of  Paris  green  has  been  used  considerably.  It  con- 
sists in  adding  a  large  amount  of  lime  to  the  water  in  which 
the  Paris  green  is  mixed,  and  this  appears  to  be  sufficient  to 
render  insoluble  any  slight  amount  of  free  arsenic  or  other  sol- 
uble arsenites  that  may  be  present.  The  use  of  lime  with  Paris 
green  has  now  come  to  be  recognized  as  a  very  important  pre- 
cautionary measure  in  preparing  this  spraying  material,  chiefly 
because  of  the  presence  of  white  arsenic  in  the  Paris  green  that 


—  12  — 

has  been  manufactured  of  late  years.  The  amount  commonly 
recommended  varies  from  one  to  ten  parts  of  lime  to  each  part 
of  Paris  green.  If  the  amount  of  free  arsenic  in  the  sample  is 
not  too  high,  good  effects  will  result  from  adding  the  lime;  but 
beyond  a  certain  point  the  lime  does  no  good  and  may  even  do 
harm.  It  has  long  been  known  that  lime  acts  on  white  arsenic, 
when  the  latter  is  in  suspension  in  water,  in  such  a  way  as  to 
render  it  much  more  injurious  to  foliage  than  the  arsenic 
would  have  been  without  the  lime. 

Tests  for  Purity. 

There  are  no  simple  tests  which  will  enable  a  person  to 
quickly  determine  absolutely  the  purity  of  any  given  sample 
of  Paris  green.  A  great  many  forms  of  adulterants,  however, 
can  be  immediately  detected.  Samples  showing  any  consider- 
able variation  in  color,  especially  an  abnormally  pale  shade, 
is  an  almost  certain  indication  of  adulteration,  and  those 
showing  a  tendency  to  dampness,  or  caking,  should  be 
rejected.  Two  or  three  methods  are  available  for  recognizing 
most  of  the  more  conspicuous  impurities. 

Ammonia  Test. — Paris  green  dissolves  freely  and  wholly  in 
ammonia,  becoming  a  beautiful  blue  liquid;  while  a  majority  of 
the  substances  formerly  used  in  adulterating  a  green  are  insol- 
uble. This,  therefore,  is  a  very  ready  means  of  recognizing 
most  of  the  crude  forms  of  adulteration.  If  upon  treatment 
with  ammonia  any  of  the  material  fails  to  dissolve,  the  sample 
is  adulterated.  This  test,  however,  is  not  conclusive,  since 
white  arsenic  and  a  number  of  other  substances  used  in  adul- 
terating Paris  green,  especially  in  these  later  years,  are  soluble 
in  ammonia  and  would  escape  detection  if  this  method  alone 
were  depended  on.  Ammonia  then  affords  valid  grounds  for 
rejecting  a  sample  if  any  portion  of  it  is  insoluble  ;  but  other 
means  must  be  used  to  be  sure  of  its  purity,  even  if  apparently 
pure   by  this  test. 

Glass  Test. — A  very  simple  test,  which  will  enable  one  to 
distinguish  quite  a  good  proportion  of  adulterated  samples  at 
once,  including  many  of  those  not  detectable  with  ammonia, 
is  to  take  a  very  small  portion  of  Paris  green — what  one  could 
easily  pick  up  on  the  point  of  a  penknife — place  this  upon  a 


—  13  — 

piece  of  glass,  holding  the  glass  at  an  angle;  jarring  the 
lower  edge  will  cause  the  little  pile  of  green  to  move  down  the 
inclined  surface,  leaving  behind  it  a  bright  green  track,  if  the 
sample  is  pure ;  but  in  the  case  of  many  adulterated  or  impure 
samples  the  track  would  be  white,  or  pale  green.  The  method 
of  doing  this  is  clearly  shown  in  the  accompanying  plate. 
The  glass  test  is  particularly  useful  in  comparing  a  number  of 
samples,  and  after  one  has  acquired  some  experience  it 
becomes  quite  reliable.  It  does  not  enable  one  to  detect  the 
recent  forms  of  arsenic  adulterations,  and  like  the  ammonia 
test,  should  never  be  considered  as  conclusive  evidence  of 
purity. 


Microscopic  Examination. — By  far  the  most  satisfactory 
of  all  the  easy  methods  for  the  testing  of  Paris  green  is  the 
use  of  the  microscope.  For  this  purpose  the  sample  is  placed 
on  a  slip  of  glass  and  treated  in  the  way  just  described  for  the 
glass  test ;  the  glass  slip  is  then  put  under  the  microscope  and 
examined  with  a  medium  power  objective,  about  one-quarter 
inch.  The  Paris  green  will  be  seen  in  the  form  of  clean,  round 
balls,  and  in  a  perfectly  pure  sample  these  are  all  that  can  be 
seen.  In  impure  samples  there  will  be  observed,  in  addition 
to  these  green  spheres,  a  considerable  quantity  of  material  of 
crystalline  or  irregular  shape,  usually  of  white  color,  the  pure 
green  being  quite  as  distinct  from  the  adulterants  as  seen 
3tjb 


—  14  — 

under  the  microscope,  and  as  easily  recognized  as  wheat  can 
be  distinguished  from  the  dirt  that  might  be  mixed  with  it. 

There  is  more  difficulty  in  distinguishing  Paris  green  con- 
taining an  excess  of  free  arsenic.  This  sometimes  is  added  in 
the  form  of  a  powder,  and  is  then  as  easily  recognized  as  any 
other  form  of  adulterant ;  but  when  added  in  the  process  of 
manufacture  it  is  firmly  attached  to  the  particles  of  Paris 
green,  and  only  produces  the  effect  of  making  them  somewhat 
irregular,  and  causing  a  tendency  toward  sticking  together. 
A  study  of  the  figure  on  the  title-page  will  enable  one  to 
distinguish  the  pure  green  from  the  adulterated  sample.  The 
size  of  the  particles  of  Paris  green  may  be  larger  or  smaller, 
according  to  the  method  of  manufacture ;  and  the  grade  of  the 
material  may  vary  greatly  and  can  only  be  properly  deter- 
mined by  chemical  tests. 

Requirements  for  Spraying  Purposes. 

Paris  green  was  originally  wholly,  and  is  still  in  part,  manu- 
factured for  use  as  a  pigment;  but  the  requirements  for  this 
material  when  used  as  a  spray  are  somewhat  different  from 
what  is  necessary  for  a  paint.  For  paint  purposes,  one  of  the 
prime  requisites  is  color;  next  to  that  perhaps,  insolubility  in 
water,  upon  which  depends  much  of  the  wearing  quality  of  the 
paint.  For  spray  purposes  the  color  amounts  to  nothing; 
insolubility  is  an  essential,  because  upon  this  depends  the 
safety  of  the  plant;  and  in  addition  to  this  there  must  be  suffi- 
cient poison  (white  arsenic  in  combination)  to  be  effective  as 
an  insecticide. 

It  has  been  known  from  the  first  that  Paris  green  is  not  a 
definite  chemical  compound,  but  may  vary  considerably  in  its 
chemical  constituents.  It  has,  however,  a  definite  physical 
structure  and  characteristics.  As  stated  above,  a  good  sample 
of  Paris  green  consists  almost  exclusively  of  clean,  round, 
green  crystalline  masses  of  uniform  size  and  appearance, 
and  with  scarcely  a  trace  of  any  foreign  matter.  While  it  may 
not  be  possible  to  make  a  Paris  green  which  is  absolutely  pure 
(that  is,  which  consists  entirely  of  these  green  spheres),  the 
older  methods  of  manufacture  produced  an  article  approaching 
very  closely  to  this  ideal.  The  Paris  green  now  in  the  market 
contains  generally  a  very  appreciable  per  cent  of  material  not 


—  15  — 

combined  in  a  way  to  show  these  characteristic  crystalline 
masses,  even  when  the  chemical  composition  approaches  very 
closely  to  the  theoretical  proportions.  One  of  the  greatest 
faults  of  the  methods  of  manufacture  now  mostly  used,  viewed 
from  the  standpoint  of  the  farmer,  is  the  diminution  in  the 
amount  of  arsenic  in  combination.  An  analysis  given  in  the 
latter  part  of  this  Bulletin,  of  a  sample  of  Paris  green  showing 
fair  color  and  which  would  possibly  be  considered  a  fairly 
satisfactory  paint  pigment,  contains  about  one  half  the  amount 
of  arsenious  oxid  that  has  been  supposed  to  be  present  in  pure 
Paris  green,  and  in  addition,  in  an  uncombined  form,  nearly 
one  quarter  of  its  weight  of  free  white  arsenic.  It  is  possible 
that  in  this  particular  case,  the  free  white  arsenic  may  have 
been  added  because  the  laws  of  New  York  require  the  total 
arsenic  to  be  at  least  fifty  per  cent.  Such  a  sample  would  be 
very  unsafe  to  apply  to  the  foliage  of  plants,  and  especially  so 
under  the  climatic  conditions  existing  in  California,  as  is 
shown  elsewhere. 

There  does  not  seem  to  be  any  evidence  that  the  larger 
manufacturers  of  Paris  green  have  intended  to  place  upon  the 
market  anything  other  than  an  acceptable  article.  The  sample 
of  Paris  green  referred  to  certainly  cost  the  manufacturer  fully 
as  much  as  one  conforming  to  the  usual  standards.  Apparently 
he  found  that  his  Paris  green  failed  to  meet  the  requirements 
of  the  law.  and  not  having  knowledge  of  the  danger  of  white 
arsenic  to  foliage,  he  added  a  sufficiency  to  meet  these 
requirements. 

Laws  Concerning  Paris  Green. 

A  number  of  the  States,  including  New  York,  Louisiana, 
Texas,  and  Oregon,  have  enacted  laws  requiring  the  Paris  green 
sold  on  the  market  in  those  States  to  contain  fifty  per  cent  of 
arsenious  oxid.  These  laws  differ  somewhat  in  detail  in  the 
different  States,  but  agree  in  establishing  this  standard  for 
purity.  Apparently,  the  only  requirements  of  the  laws  in  any 
of  these  States  is  that  the  substance  sold  as  Paris  green  shall 
contain  at  least  this  minimum  amount  of  arsenious  oxid. 
Since  arsenic  is  the  cheaper  ingredient  in  Paris  green,  it  is 
evident  that  this  law  could  be  taken  advantage  of  by  the 
manufacturers  or  dealers  and  an  inferior  article  placed  on  the 
market,  containing  any  combination  of  material  so  long  as  it 


—  16  — 

is  green  and  contains  sufficient  of  this  comparatively  cheap 
substance. 

There  is  nothing  in  the  laws,  nor  has  there  been  any 
attempt  by  the  chemists  in  charge  of  the  analyses  made 
under  the  laws,  to  distinguish  the  amount  of  uncombined,  or 
soluble,  arsenious  oxid  in  the  substances  sold  as  Paris  green. 
Such  laws  may  be  satisfactory  to  manufacturers  or  dealers,  but 
certainly  leave  very  much  to  be  desired  from  the  standpoint 
of  fruit-growers  or  agriculturists  in  whose  benefit  they  are 
supposed  to  have  been  enacted;  they  show  evidence  of  the  fail- 
ure to  appreciate  the  real  situation  by  those  who  frame  the 
laws.  In  most  of  these  States  the  laws  are  well  provided  with 
means  to  secure  their  enforcement,  so  that  by  remedying  the 
defect  pointed  out  above,  by  the  establishment  of  a  truer 
standard  of  purity,  the  markets  would  again  be  filled  with  a 
satisfactory  Paris  green.  Manufacturers  are  not  so  blind  to  their 
own  interests  as  to  fail  to  meet  any  clearly  defined  demand. 
They  stand  anxious  and  ready  to  meet  any  reasonable  require- 
ment the  fruit-grower  may  make. 

Standards  of  Purity  and  Quality. 

It  is  evident  from  what  has  been  said  in  the  above  discussion, 
that  the  chemical  analysis  which  simply  shows  the  total  per 
cent  of  arsenious  oxid  is  not  a  sufficient  criterion  either  for 
purity  or  quality  in  Paris  green.  Arsenic  is  certainly  the 
active  principle,  and  everything  else  being  equal  the  effective- 
ness of  the  insecticide  is  directly  proportional  to  the  quantity 
of  arsenic  present.  The  different  arsenical  compounds  have 
each  a  somewhat  different  degree  of  efficiency,  and  the  poison- 
ous effects  differ  more  or  less  also  with  each  insect  and  plant. 

The  difference  in  efficiency  of  the  various  compounds  is  in  a 
good  measure  dependent  upon  the  chemical  and  physical  con- 
dition of  the  arsenic  in  the  various  combinations.  For  instance, 
the  killing  qualities  of  Paris  green  and  arsenate  of  lead,  when 
used  against  the  gypsy-moth,  even  when  the  amounts  of  arsenic 
present  in  the  two  applications  are  equal,  are  quite  appre- 
ciably different.  It  will  be  necessary,  therefore,  that  the  exact 
condition  of  the  arsenic  in  a  spraying  compound  be  specified 
and  determined.  The  presence  of  free  arsenious  oxid,  or  of 
arsenic  in  any  soluble  form,  should  be  determined  in  every  case, 


—  17  — 

because  it  is  a  particularly  dangerous  impurity.  In  the  case  of 
such  substances  as  Paris  green  which  have  no  definite  chemical 
formula  the  character  of  the  material  can  be  best  determined 
by  microscopic  examination,  confirmed  always,  of  course,  by 
a  chemical  test.  To  pass  as  satisfactory,  the  microscope  should 
show  the  proper  crystalline  forms  as  composing  practically  all 
of  the  substance.  In  addition  to  this  there  should  be  an 
entire  absence  of  all  free  arsenious  oxid,  and  the  Paris  green 
should  be  of  sufficiently  high  grade;  that  is,  one  containing 
a  sufficiently  large  amount  of  arsenious  oxid  in  combination. 
Exactly  what  this  grade  should  be  is  a  matter  which  deserves 
some  consideration. 

When  a  Paris  green  can  be  made  containing  nearly  sixty  per 
cent  of  combined  arsenious  oxid,  and  another  containing  not 
over  forty  per  cent,  it  is  evident  that  very  different  results  will 
be  obtained  by  the  use  of  the  two  forms,  as  it  would  take  three 
pounds  of  forty  per  cent  green  to  equal  the  effectiveness  of  two 
pounds  of  sixty  per  cent.  The  laws  in  the  Eastern  States  have 
uniformly  adopted  fifty  per  cent  as  the  standard,  and  possibly 
it  would  be  well  to  retain  this  as  the  standard,  though  it  would 
seem  better,  in  order  to  secure  greater  uniformity,  to  make  the 
standard  fifty-five  per  cent;  or  to  treat  Paris  green  in  the  same 
way  that  fertilizers  are  treated,  viz:  have  the  percentage  certified 
to  and  stated  on  the  samples,  so  that  forty,  fifty,  fifty-five,  or 
sixty  per  cent  might  be  sold  on  the  market,  each  grade  under  its 
proper  label.  This  is  a  matter,  however,  that  wTill  have  to  be 
decided  after  a  more  careful  consultation  between  the  interests 
involved.  For  the  present,  the  standard  which  this  Department 
will  require  in  samples  of  Paris  green  is : 

First — The  sample  will  be  expected  to  contain,  as  seen  under 
the  microscope,  only  a  trace  of  foreign  matter; 

Second — That  the  total  of  arsenious  oxid  shall  exceed  fifty 
per  cent; 

Third — That  the  samples  shall  contain  practically  no  free 
arsenic  or  other  soluble  arsenical  compounds. 

Substitutes  for  Paris  Green. 

A  good  sample  of  Paris  green  is  a  satisfactory  article  for 
killing  codling-moth,  and  it  has  been  tested  so  long  under  all 
sorts  of  conditions,  and  proven  itself  thoroughly  satisfactory; 
and,  moreover,  as  it  can  be  had  everywhere  and  requires  no 


—  18  — 

preparation,  it  is  altogether  an  extremely  satisfactory  remedy 
to  use.  The  unreliability  of  the  substance,  however,  is  such 
that  unless  one  is  assured  of  the  quality  of  the  sample  he 
intends  to  use,  the  only  safe  procedure  is  to  use  one  of  the 
substitutes  hereinafter  described.  Not  only  the  unreliability 
but  also  the  cost  of  Paris  green  has  caused  many  to  look  for  a 
substitute.  This  search  has  been  sufficiently  successful  to  in- 
cline many  to  the  opinion  that  Paris  green  never  can  again  take 
the  almost  exclusive  place  it  formerly  held  among  this  class  of 
insecticides.  A  number  of  compounds  have  been  suggested 
and  more  or  less  thoroughly  tried  for  this  purpose,  and  the 
results  obtained  in  some  cases  have  been  very  highly  satisfac- 
tory. There  are  quite  a  number  of  substances  of  this  character 
already  on  the  market,  and  some  can  be  very  easily  and  cheaply 
manufactured  at  home. 

READY-MADE    COMPOUNDS. 

The  convenience  of  being  able  to  apply  an  insecticide  without 
any  preliminary  preparation  will  always  favor  a  ready-made 
as  compared  to  a  home-made  article.  Very  few  of  those  now  on 
the  market  have  been  sufficiently  tested  for  the  codling-moth  to 
enable  us  to  recommend  them,  but  they  might  be  well  worthy 
of  trial  in  a  small  way  by  the  orchardist.  It  should  be  under- 
stood, however,  that  at  the  present  time  we  have  no  assurance 
that  these  ready-made  substances  are  uniform  or  will  remain 
uniform  in  composition  and  efficiency.  As  with  Paris  green,  a 
standard  of  excellence  should  be  established  and  maintained 
by  law. 

COPPER    COMPOUNDS. 

The  simple  arsenite  of  copper  usually  known  as  Scheele's 
green  has  been  used  and  recommended  quite  highly  as  a  sub- 
stitute for  Paris  green.  When  pure  it  has  a  definite  composi- 
tion and  crystallizes  into  smaller  crystals,  and  in  both  of  these 
respects  being  distinctly  better  than  Paris  green.  There  seems 
no  reason  why  it  might  not  be  entirely  satisfactory  for  codling- 
moth  work,  though  I  have  no  data  in  regard  to  its  effectiveness 
for  this  purpose. 

Other  forms  of  this  compound  have  been  sold  under  the 
names  of  Paragrene,  Green  arsenite,  Green  arsenoid,  and 
Laurel  green.     Of  the  first  two  I  have  favorable  reports  from 


—  19  — 

Maine  and  New  York.  Green  arsenoid  has  proven  in  our 
hands  rather  injurious  to  foliage,  and  Laurel  green  did  not 
prove  satisfactory  in  the  hands  of  Professor  Harvey  of  Maine. 
Some  of  these  are  very  far  from  being  pure  arsenite  of  copper. 

BARIUM    COMPOUNDS. 

Barium  arsenite  is  not  uncommonly  used  as  an  adulterant 
in  Paris  green.  Under  the  name  "white  arsenoid"  it  is  sold 
for  spraying  purposes.  Samples  examined  by  us  were  very 
unsatisfactory,  being  very  soluble  and  injurious  to  foliage. 
There  seems  to  be  no  reason  why  it  might  not  be  all  right  if  it 
is  practicable  to  make  it  insoluble. 

LIME    COMPOUNDS. 

London  purple  is  the  oldest  of  the  Paris  green  substitutes  on 
the  market.  It  is  an  arsenite  of  lime  produced  as  a  by- 
product in  the  manufacture  of  aniline  dyes,  and  contains  cer- 
tain organic  material  which  gives  to  it  the  purple  color.  It 
has  been  quite  extensively  used  for  codling-moth,  and  has  gen- 
erally been  considered  an  exact  equivalent  of  Paris  green  in 
its  effectiveness.  It  often  contains  considerable  free  white 
arsenic,  sometimes  to  such  an  extent  as  to  make  it  excessively 
injurious  to  foliage,  and  for  this  reason,  more  than  for  any 
other,  it  has  nearly  dropped  out  of  use  in  a  large  part  of  the 
country.  It  has  a  definite  advantage  over  Paris  green  in  its 
lighter  weight  and  finer  grain,  which  enables  it  to  remain  in 
suspension  in  the  water  very  much  better,  and  therefore  more 
likely  to  be  evenly  distributed.  Were  it  not  for  the  danger  to 
the  foliage,  London  purple  could  be  highly  recommended  for 
codling-moth  work. 

Arsenite  of  Lime. — The  simple  arsenite  of  lime  seems  to  be 
the  only  substance  besides  London  purple  that  has  been  exten- 
sively tried  for  codling-moth.  Professor  Lowe,  of  New  York, 
writes:  "Some  of  the  leading  growers  in  this  vicinity  used  the 
arsenite  of  lime  last  season  with  excellent  results. "  Professor 
Slingerland  says:  "I  have  reports  from  some  of  our  best  fruit- 
growers that  they  have  found  the  arsenite  of  lime  even  more 
effectual  than  Paris  green,  and,  of  course,  a  great  deal  cheaper." 

In  Michigan,  where   the  arsenite   of  lime   has   been   more 


—  20  — 

extensively  used  than  elsewhere,  it  seems  to  have  been  very 
satisfactory.  Professor  Taft  writes:  "I  began  nearly  five  years 
ago  to  recommend  the  use  of  arsenic,  owing  to  its  superior 
cheapness.  As  a  rule,  the  price  of  arsenic  as  compared  with 
that  of  Paris  green  has  rendered  it  about  one  sixth  as  expen- 
sive, and,  although  I  would  not  go  so  far  as  you  do  regarding 
impurities  in  Paris  green,  I  am  sure  that  the  danger  of  finding 
adulterations  in  arsenic  will  be  much  less.  I  first  began  the 
use  of  arsenic  in  an  extensive  way  upon  the  college  orchards 
(nearly  fifty  acres)  in  1895,  and  have  used  it  ever  since,  buy- 
ing it  at  the  rate  of  a  hundred  pounds  at  a  time  and  employing 
it  also  upon  potatoes  and  all  other  crops  upon  which  I  formerly 
used  Paris  green.  While  arsenite  of  lead  proved  effective  and 
less  likely  to  injure  the  foliage  than  Paris  green,  when  the 
latter  was  used  in  water  without  lime,  its  cost  made  it,  in  our 
minds,  far  less  desirable  than  arsenite  of  lime,  or  even  Paris 
green  when  the  latter  was  used  with  lime." 

Professor  Brunner,  of  Nebraska,  writes:  "We  have  not  thus 
far  had  much  experience  with  the  arsenites  of  lime  or  lead, 
but  seem  to  have  better  results  with  the  former  than  with  Paris 
green." 

In  Oregon  arsenite  of  lime  seems  to  have  been  extensively 
used  of  late.  Professor  Cordley  writes:  "We  have  given  but 
little  attention  to  the  various  substitutes  for  Paris  green.  On 
a  small  scale,  however,  we  have  tested  both  the  arsenite  of 
lime  and  the  arsenite  of  soda  (Kedzie's)  mixture,  and  have 
found  them  satisfactory.  Owing  to  the  high  price  of  Paris 
green  many  of  our  Hood  River  apple-growers  have  used  the 
arsenite  of  soda  for  the  past  two  years,  and  have  yet  to  hear 
any  complaint  regarding  it.  Mr.  Williamson,  of  Portland, 
writes:  "I  would  say  that  a  considerable  number  of  fruit- 
growers in  Oregon  and  Washington  have  used  arsenite  of  lime 
as  a  substitute  for  Paris  green,  and  in  every  case,  so  far  as  I 
have  heard,  with  satisfactory  results.  It  has  been  found  to  be 
fully  as  effective  as  good  Paris  green  and  much  cheaper." 
Hon.  E.  L.  Smith,  of  Hood  River,  writes:  "I  saved  ninety-five 
per  cent  of  apples  free  from  codling-moth,  and  one  of  my  neigh- 
bors did  even  better  than  that." 

Professor  Hedrick,  of  Utah,  writes:  "We  have  used  arsenite 
of  lime  at  this  station  for  two  seasons  with  marked  success." 


—  21  — 

It  will  thus  appear  that  arsenite  of  lime  has  been  quite 
thoroughly  tested  and  with  the  best  of  results.  In  most  cases 
the  home-made  article  was  used.  A  number  of  dealers  have 
arsenite  of  lime  on  the  market,  and  if  one  could  be  assured  of 
its  quality  there  seems  to  be  no  reason  why  they  should  not 
replace  Paris  green,  on  the  score  of  cheapness. 

LEAD    COMPOUNDS. 

Arsenite  and  Arsenate  of  Lead. — These  compounds  are  used 
in  Massachusetts  by  the  Gipsy-Moth  Commission  as  a  substitute 
for  Paris  green,  as  the  latter  appears  to  be  particularly  ineffec- 
tive when  used  for  the  gipsy-moth  larva.  Arsenate  of  lead  is 
distinctly  better  for  these  larvse  than  the  arsenite,  though  both 
substances  Have  been  extensive^  experimented  with  in  all  of 
the  New  England  and  Middle  States.  Professor  Britton,  of 
Connecticut,  writes:  "Have  prepared  and  used  arsenate  of 
lead  with  good  results.  I  cannot  testify  as  to  its  effective- 
ness against  the  codling-moth,  but  expect  it  to  prove  satis- 
factory against  any  eating  insect  where  Paris  green  is  commonly 
used."  Professor  Slingerland  writes:  "The  arsenate  of  lead  is 
being  quite  extensively  used  in  Albany  and  possibly  in  some 
other  places  in  Hudson  River  valley  for  the  elm-leaf  beetle.  I 
do  not  know  that  any  one  has  used  the  arsenate  of  lead  in  this 
State  for  the  codling-moth."  Professor  Smith,  of  New  Jersey, 
has  for  years  recommended  the  use  of  arsenate  of  lead,  but  gives 
no  data  regarding  its  effectiveness  for  the  codling-moth;  like- 
wise, Professor  Butz,  of  Pennsylvania,  notes  that  it  is  an  effectual 
substitute  for  Paris  green,  but  has  not  used  it  on  apples  for  the 
codling-moth.  The  same  is  true  of  Professor  Quaintance,  of 
Georgia.  Professor  Garman,  of  Kentucky,  writes:  "I  have 
used  arsenate  of  lead  and  consider  it  a  useful  addition  to  our 
insecticides,  because  of  the  ease  with  which  it  can  be  kept  in 
suspension;  also  because  it  can  be  used  very  strong  without 
injury  to  foliage.  Some  insects,  such  as  grasshoppers  and 
blister-beetles,  are  not  easily  killed  with  the  ordinary  mixtures 
of  Paris  green.  The  arsenate  of  lead  is  a  convenient  substitute 
for  such  cases  when  it  can  be  used  without  danger  to  man." 
Similar  reports  come  from  Professor  Webster,  of  Ohio,  who  used 
it  against  the  fldia  of  the  grapevine.  Professor  Stedman,  of 
Missouri,  writes  as  to  arsenate  of  lead  and  arsenite  of  lime:  "  I 


—  22  — 

have  found  no  difficulty  whatever  in  using  them  wherever  Paris 
green  will  prove  valuable.  So  far  as  I  can  see  they  can  be  used 
as  a  perfect  substitute." 

HOME-MADE    COMPOUNDS. 

The  cheapest  arsenical  compounds  are  certainly  home-made 
mixtures.  The  method  of  manufacture  of  these  substances  is 
very  simple,  and  there  seems  to  be  no  reason  why  they  might 
not  be  used  almost  exclusively. 

Arsenate  of  Lead  has  not  been  tried  for  the  codling-moth,  as 
reports  received  in  answer  to  our  circular  show,  but  the  highly 
satisfactory  results  obtained  upon  other  insects  and  the  per- 
fect safety  to  foliage  would  indicate  that  it  might  be  extremely 
profitable  to  experiment  with.  There  are  two  methods  of 
making  arsenate  of  lead,  which  produce  substances  somewhat 
different  in  chemical  structure,  but  about  equally  effective.  In 
each  method  sixty-eight  per  cent  of  arsenate  of  soda  is  used, 
and  with  this,  in  one  case,  the  ordinary  white  granular  acetate 
of  lead,  and  in  the  other,  lead  nitrate.  The  process  of  manu- 
facture is  as  follows  :  The  lead  salt  and  arsenate  of  soda  are 
dissolved  separately,  and  then  poured  into  the  tank  containing 
the  water  for  spraying.  The  proportions  used  are  about  as 
follows  :  For  every  ten  ounces  of  arsenate  of  soda  take  twenty- 
four  ounces  of  lead  acetate  or  twenty  ounces  of  lead  nitrate. 
These  substances  can  be  purchased  in  the  right  proportions 
and  tied  up  in  bags,  so  that  it  will  take  one  bagful  of  each  for 
each  tank  of  water. 

The  amounts  given  above  are  sufficient  to  make  about  a  pound 
of  the  pure  arsenate  of  lead,  which  would  probably  be  enough 
for  one  hundred  and  fifty  or  two  hundred  gallons  of  water.  It 
can  be  used  with  perfect  safety  several  times  as  strong  as  this. 
As  a  precautionary  matter,  it  might  be  well  to  test  the  mixture 
in  order  to  be  sure  that  the  arsenic  is  all  in  combination,  which 
can  be  done  by  the  use  of  potassium  bi-chromate,  which  will 
produce  a  yellow  precipitate  if  the  solution  contains  lead  in 
excess,  as  it  should. 

Arsenic  and  Lime. — Very  satisfactory  directions  for  making 
this  mixture  are  given  in  a  letter  from  Professor  Taft,  of  Michi- 
gan, one  of   the  first  who  extensively  experimented  with  it; 

ERRATUM. 
In  line  1(5  (above)  omit  of;   reference  being  made  to  the  common,  com- 
fi«%  ffrade  of  arsenate  of  soda. 


VTlOWO'l 


—  23  — 

he  writes :  "I  have  had  excellent  results  from  boiling  one  pound 
of  [white]  arsenic  and  two  pounds  of  lime  in  two  gallons  of 
water  for  forty  minutes  and  then  diluting  as  required. 
When  one  pound  of  the  arsenic  prepared  as  above,  is  used  in 
every  three  hundred  to  four  hundred  gallons  of  water,  I  have 
found  it  equal  to  Paris  green  for  destroying  codling-moth  and 
curculio,  while  one  pound  answers  for  one  hundred  and  fifty 
to  two  hundred  gallons  of  water  when  it  is  used  upon  potatoes; 
unless  used  in  Bordeaux  mixture,  I  find  it  best  to  add  a  small 
amount  of  lime  when  diluting.  As  the  wholesale  price  of 
arsenic  has  averaged  about  seven  cents  per  pound  for  a  number 
of  years,  while  Paris  green  has  wholesaled  at  eighteen  cents, 
it  is  evident  that  the  latter  is  fully  five  times  as  expensive." 
In  reference  to  the  comparative  value  of  arsenic  with  soda  and 
lime,  he  further  writes :  "While  some  recommend  the  use  of 
sal-soda  to  dissolve  the  arsenic,  we  have  not  found  it  neces- 
sary; and  as  the  use  of  soda  at  the  rate  commonly  recom- 
mended nearly  doubles  the  expense  of  the  spraying  mixture, 
we  have  not  recommended  it,  although  the  claim  that  when 
sal-soda  is  used  it  is  possible  to  tell  when  the  arsenic  is  dis- 
solved, is  correct."  The  only  trouble  with  this  mixture  seems 
to  be  the  danger  of  an  incomplete  union  between  the  lime  and 
the  arsenic,  so  that  the  full  forty  minutes'  boiling,  possibly 
even  with  .more  lime  and  the  addition  of  lime  when  diluting, 
would  probably  render  the  mixture  entirely  safe. 

Arsenic,  Soda,  and  Lime. — This  is  often  known  as  the  Kedzie 
formula,  as  it  seems  first  to  have  been  recommended  by  Pro- 
fessor Kedzie,  of  Michigan.  The  method  of  its  production  is 
fully  described  in  the  following  letter  from  Professor  Kedzie: 

Agricultural  College,  Michigan, 
September  5,  1899. 
The  formula  I  recommended  for  an  arsenical  spraying  mixture  to  take  the 
place  of  Paris  green  was  the  following :  Boil  two  pounds  of  white  arsenic 
with  eight  pounds  of  sal-soda  in  two  gallons  of  rain  water.  Boil  these 
materials  together  in  any  iron  pot  not  used  for  other  purposes ;  boil  them 
fifteen  minutes,  or  until  the  arsenic  dissolves,  leaving  only  a  small  muddy 
sediment.  Put  the  solution  in  a  two-gallon  jug  and  label  Poison,  Stock 
Material  for  spraying  mixture.  The  spraying  mixture  can  be  prepared  when- 
ever required  in  the  quantity  needed  at  the  time,  by  slacking  two  pounds  of 
lime,  and  adding  this  to  forty  gallons  of  water ;  pour  into  this  a  pint  of 
the  stock  arsenic  solution ;  mix  up,  stirring  thoroughly,  and  the  spraying 
mixture  is  ready  for  use.  The  arsenic  in  this  mixture  is  equivalent  to  four 
ounces  of  Paris  green. 


—  24  — 

Advantages  of  this  Method:  First— It  is  very  cheap  and  the  materials 
can  be  found  in  every  village  in  the  State ; 

Second— The  stock  material  (arsenite  of  soda)  is  easily  prepared  and  can 
be  kept  in  that  form  for  any  length  of  time,  ready  for  making  a  spraying  mix- 
ture of  lime  and  water ; 

Third— The  arsenite  of  lime  in  the  quantity  required  for  spraying  will  not 
burn  the  leaves,  or  injure  the  trees  or  plants ; 

Fourth — It  will  be  uniform  in  quality  and  not  vary  in  strength,  as  Paris 
green  often  does ; 

Fifth— It  makes  a  milky  colored  spray  and  the  color  on  the  trees  will  show 
how  evenly  it  is  distributed. 

Every  one  using  such  deadly  poison  should  bear  in  mind  the  possible 
danger  from  its  use;  the  pot,  the  jug,  and  every  apparatus  for  making  the 
arsenite  of  soda  should  be  used  for  no  other  purpose  of  any  kind. 

Yours  faithfully, 

(Signed:)    R.  C.  KEDZIE. 

Mr.  Smith,  of  Hood  River,  Oregon,  varies  this  formula, 
recommending:  "Instead  of  two  pounds  of  lime  I  used  not  less 
than  six  pounds;  and  I  found  that  the  additional  lime  pre- 
vented burning  foliage  and  also  retained  the  poison  longer  on 
the  trees.  I  also  used  one  quart  instead  of  one  and  a  half  pints 
of  the  arsenic  to  fifty  gallons  of  water."  And  again,  "I  would 
recommend  using  freely  of  the  lime  up  to  say  ten  pounds  to 
fifty  gallons  of  water." 

Danger  from  the  Use  of  Arsenical  Mixtures. — It  should  be 
borne  in  mind  that  arsenic  is  a  very  dangerous  poison  and 
that  in  any  form  it  may  be  fatal  to  man  or  animals;  especially 
should  care  be  taken  in  the  manufacture  of  the  home-made 
compounds,  as  the  handling  necessary  in  these  cases  increases 
the  danger  from  poisoning  through  carelessness.  Properly 
handled,  arsenic  is  perfectly  harmless,  and  there  is  no  excuse 
for  any  one  becoming  in  any  way  affected  by  it.  There  is  in 
the  minds  of  a  few  people  some  apprehension  that  bad  results 
might  follow  from  the  use  of  fruit  protected  by  spraying;  but 
this  apprehension  is  certainly  without  foundation.  There  is 
yet  to  be  the  first  case  of  injury  resulting  in  this  way.  In 
all  reported  cases  that  have  come  under  our  observation  the 
symptoms  were  in  no  case  anything  like  those  that  might  be 
produced  by  the  arsenic.  It  is,  nevertheless,  true  that  a  certain 
amount  of  arsenic  remains  on  the  fruit,  and  that  no  one  sprays 
any  considerable  time  with  the  arsenites  without  getting  some 
of  the  material  into  the  mouth  or  lungs;  in  some  cases  even 
enough  to  be  recognized  in  the  excretions.  We  have  known  a  few 
cases  in  which  the  person  applying  the  poison  was  careless 


—  25  — 

enough  to  become  very  slightly  affected  by  the  symptoms  of 
chronic  arsenic  poisoning.  These  cases  simply  show  the  need 
of  great  care  in  handling  the  poisons,  though  this  can  be  done 
with  perfect  safety  when  care  is  taken. 

Other  Methods  of  Fighting  the  Codling-Moth. 

Before  the  introduction  of  Paris  green  for  the  codling-moth  a 
number  of  methods  were  more  or  less  generally  used  for  com- 
bating this  insect. 

The  Band  Treatment. — Foremost  among  these  was  the  band 
treatment;  this  became  generally  discarded,  however,  for  the 
reason  that  sufficiently  satisfactory  results  could  be  obtained 
by  the  use  of  the  poison  alone,  and  that  when  this  was  used  the 
amount  of  added  protection  offered  by  the  use  of  the  band 
method  was  not  sufficient  to  counterbalance  the  cost  of  apply- 
ing the  bands.  Of  late  years,  due  to  less  satisfactory  results 
with  the  Paris  green,  interest  in  the  band  treatment  has  been 
revived  and  not  a  few  orchardists  are  using  the  two  methods 
together. 

The  band  treatment  consists  in  applying  around  the  trunk 
of  the  tree,  or  on  the  larger  branches,  a  band  made  of  a  part  of 
a  grain  sack  or  other  similar  material  which  affords,  in  its 
folds  and  between  it  and  the  bark,  very  attractive  places  for 
the  insect  to  hide  when  ready  to  transform  into  the  pupa  stage. 

After  bands  are  applied  it  is  necessary  to  examine  each  at 
least  once  in  two  or  three  weeks,  and  to  destroy  by  hand 
all  the  larvae  and  pupse  found  in  them.  This  is  a  somewhat 
tedious  operation;  it  requires  a  great  deal  of  time  to  get  over  a 
large  orchard,  and  there  seems  to  be  a  considerable  danger  of 
overlooking  some  of  the  insects.  Again,  the  operation  must  be 
continuously  attended  to,  or  the  results  will  be  worse  than 
though  the  bands  were  not  used  at  all,  because  they  afford 
such  favorable  hiding-places  that  the  codling-moth  is  very  much 
more  apt  to  escape  birds  and  other  natural  enemies. 

Some  orchardists  have  adopted  the  plan  of  removing  the  band, 
killing  the  insects  that  are  on  the  bark,  and  replacing  it  with  a 
new  piece  of  cloth,  the  old  bands  being  gathered  in  a  wagon  and 
taken  to  a  place  where  they  can  be  thoroughly  disinfected  by 
running  through  a  wringer,  by  the  use  of  heat,  or  by  means  of 
chemicals.     This  method  would  seem  to  increase  the  proba- 


—  26  — 

bility  of  thorough  work  and  probably  greatly  increase  the  speed 
and,  therefore,  cheapen  the  process. 

It  is  still  a  question  whether  the  band  treatment  is  worth 
the  trouble  when  the  Paris  green  spray  is  properly  used;  but  it  is 
altogether  likely  that  when  the  Paris  green  is  doubtful  in 
quality,  or  from  other  causes  unsatisfactory  results  are  being 
obtained  with  the  poison,  it  would  well  pay  the  cost  of  the 
treatment. 

Destruction  of  Windfalls. — Next  to  the  band  treatment  the 
most  favorite  remedy  in  the  olden  days  was  provision  for  the 
daily  destruction  of  the  windfalls,  whereby  a  large  proportion 
of  the  worms  contained  therein  would  be  destroyed  before  they 
left  the  fruit.  One  of  the  simple  methods  of  accomplishing 
this  was  the  use  of  sufficient  droves  of  hogs  in  the  orchard  to 
keep  the  windfalls  eaten  up  ;  others  made  a  practice  of  gather- 
ing the  apples  daily  and  making  them  into  cider,  which  will 
accomplish  the  death  of  the  worms  contained.  When  it  was 
not  feasible  to  make  the  fruit  into  cider  the  destruction  of  the 
worms  was  accomplished  by  placing  the  apples  in  barrels, 
covered  with  a  wire  mosquito  net.  This,  however,  will  not 
entirely  prevent  the  escape  of  the  worms,  so  the  addition  of  a 
quantity  of  grain  sacks  above  the  apples,  and,  perhaps,  a  band 
around  the  outside  of  the  barrel,  might  cause  them  to  pupate 
in  these  traps.  We  think  there  are  a  few  who  still  practice  the 
destruction  of  the  windfalls  for  the  codling-moth,  but  like  the 
band  treatment  there  is  a  great  deal  of  doubt  if  the  process  is 
profitable  when  the  poison  is  used;  used  alone  it  certainly  does 
not  protect  the  crop  as  well  as  even  a  poor  spraying  of  poison. 
If  the  utilization  of  the  windfalls  will  pay  for  the  cost  of  their 
gathering,  there  is  no  doubt  that  it  will  aid  in  the  protection 
against  the  codling-moth. 

Destruction  in  Storage  Houses. — A  great  many  apples  go 
into  the  fruit-house  with  the  worms  in  them  in  various  stages 
of  development,  and  these  escape  and  transform  into  their 
perfect  adult  condition  in  the  fruit-house  and  then  fly  back  to 
the  orchards  to  continue  their  work.  By  some  simple 
expedients,  such  as  the  use  of  screens  over  the  windows,  a 
great  majority  of  them  can  be  kept  within  the  house  and  starved 
to  death,  with  a  corresponding  advantage  in  the  protection  of 
the  succeeding  crop. 


—  27  — 

Traps. — A  great  many  traps  have  been  devised  for  the 
destruction  of  the  codling-moth.  They  have  generally  been  in 
the  form,  or  some  modification,  of  the  band.  Most  of  the  traps 
have  been  proprietary  devices  and  have  had  but  little  use, 
chiefly  on  account  of  the  expense  attendant  upon  their  appli- 
cation. The  plan  which  seems  to  be  the  most  feasible  is  to 
place  a  band  upon  the  tree  over  which,  at  a  short  distance, 
there  is  placed  a  covering  of  wire  net;  the  idea  being  that  the 
worm  can  pass  readily  through  the  meshes  of  the  net,  will 
hide  beneath  the  band,  there  go  through  its  transformation, 
and  the  moth  produced  will  not  be  able  to  make  its  escape. 
At  best,  the  use  of  these  traps  cannot  be  more  effective  than  the 
use  of  the  simple  band  alone,  so  that  they  will  not  be  satis- 
factory if  used  alone.  It  is  possible  that  when  used  with  the 
arsenical  spray  they  may  be  a  supplementary  procedure,  which 
will  be  as  effective  and  possibly  cheaper  than  bands  with  their 
regular  visitation. 

Other  forms  of  traps  have  been  devised;  such  as,  for  instance, 
lures  for  the  moth,  viz:  lantern  traps,  sweets,  etc.;  but  there 
seems  to  be  no  evidence  that  any  of  these  have  been  of  the 
slightest  value,  since  the  codling-moth  seems  to  be  very  little 
attracted  by  anything  that  has  been  tried  for  this  purpose. 

Scraping  the  Bark. — The  practice  of  scraping  the  bark  in 
the  winter  and  the  destruction  of  the  insects  attempting  to  pass 
the  season  upon  it  has  been  used  to  some  extent.  The  difficulty 
in  this  method  is  the  fact  that  only  a  small  proportion  of  the 
insects  pass  the  winter  on  the  bark,  so  that  while  many  may 
be  killed,  the  practice  alone  will  accomplish  but  little. 

Winter  Sprays. — There  have  been  many  spraying  mixture's 
advertised  as  effective  against  the  codling-moth,  which  are  to  be 
applied  in  the  winter  time.  These  are  only  referred  to  here  to 
call  attention  to  the  fact  that  they  can  be  only  of  the  slightest 
value,  and  are  chiefly  used  by  those  having  complete  ignorance 
of  the  life  history  of  the  insect  they  desire  to  combat.  Another 
similar  insect  in  this  State  which  attacks  mostly  stone  fruits, 
the  well-known  "peach  moth,"  can  be  to  some  extent  controlled 
by  winter  treatment,  but  the  habits  of  this  insect  are  essen- 
tially different  from  those  of  the  codling-moth. 


—  28  — 

Mistakes  Commonly  Made. 

All  of  the  trouble  with  the  codling-moth  is  certainly  not  due 
to  the  character  of  the  Paris  green.  A  great  many  orchardists, 
even  in  this  State,  have  no  very  clear  idea  of  the  action  of 
Paris  green,  nor  of  the  methods  of  its  application.  It  will  be 
well,  therefore,  to  point  out  some  of  the  most  common  miscon- 
ceptions and  causes  of  failure. 

One  Application  Not  Enough. — The  fact  that  most  of  our 
scale  insects  can  be  sufficiently  controlled  by  one  application 
seems  to  have  fostered  the  idea  that  all  insects  can  be  con- 
trolled thus  easily.  In  very  early  fruit,  the  earliest  pears  for 
instance,  there  are  many  localities  in  the  State  where  one  appli- 
cation at  the  proper  time  may  be  all  that  is  needed,  but  in 
most  situations,  and  always  upon  late  fruit,  repeated  spraying 
during  the  summer,  at  three  or  four  weeks  apart,  according  to 
the  locality,  will  be  found  necessary  in  order  to  obtain  the  best 
results. 

In  the  case  of  scale  insects,  the  insect  is  upon  the  plant 
and  exposed  to  the  action  of  the  insecticide  all  the  year,  but 
the  codling-moth  can  only  be  killed  during  a  very  small  part 
of  its  life;  that  is,  between  the  time  of  the  hatching  of  the  egg 
and  the  entrance  of  the  worm  into  the  fruit.  Now  the  period  of 
egg-laying  varies  very  greatly;  but,  as  a  usual  thing,  occurs  not 
far  from  the  close  of  the  blooming  period,  so  that  the  first  crop 
of  worms  can  usually  be  destroyed  by  an  application  made 
just  as  the  petals  are  falling.  In  almost,  or  quite  all  of  our 
apple  and  pear  regions,  the  codling-moth  has  many  broods;  and 
in  the  latter  part  of  the  year,  because  of  the  different  length 
of  life  of  the  different  individuals,  egg-laying  is  almost  con- 
tinuous, so  that  it  is  essential,  especially  toward  the  latter  part 
of  the  year,  to  maintain  continuously  a  coating  of  the  poison 
over  the  fruit  and  foliage.  This  requires  repeated  sprayings, 
and  especially  so  in  the  latter  part  of  the  year. 

Sprayings  Must  Be  Uniform. — Lack  of  uniformity  in  spray- 
ing will  result  in  leaving  too  much  of  the  plant  poorly 
protected,  and  so  greatly  increase  the  danger  due  to  the 
codling-moth.     Irregularity  can  occur  in  three  ways: 

First — In  the  spraying,  unless  care  is  taken,  parts  of  the 
plant  will  not  be  sufficiently  wetted.     This  is  likely  to  occur 


—  29  — 

in  the  case  of  tall  trees  near  the  top,  and  in  large  trees  toward  the 
center.  There  is  generally  a  sufficient  number  of  codling-moths 
about  to  do  a  large  amount  of  injury,  so  that  the  poor  spraying 
of  a  part  of  the  tree  is  very  liable  to  result  in  a  great  deal  of 
loss  from  the  moth.  Spraying  should  be  looked  upon  as  an 
operation  requiring  the  most  careful  and  conscientious  work, 
and  only  those  capable  of  working  in  that  way  should  be 
permitted  to  hold  the  nozzle. 

Second — Too  much  spraying  is  as  bad  as  too  little  spraying. 
Paris  green  is  so  heavy  that,  if  one  continues  to  spray  a  leaf 
after  it  is  thoroughly  wetted,  in  such  a  way  as  to  cause  the 
minute  drops  covering  the  leaf  to  run  together  and  accumu- 
late on  the  lower  edge,  or  drop  off,  he  is  sure  in  this  way  to 
wash  off  a  large  per  cent  of  the  Paris  green,  or  to  accumulate 
it  along  the  lower  edge  of  the  leaf,  where  it  will  be  of  scarcely 
any  value.  This  fact  emphasizes  the  necessity  of  care  in 
spraying,  in  order  that  no  part  shall  be  oversprayed  before  the 
other  parts  are  sufficiently  treated. 

Third — Care  must  be  exercised  at  the  pump  to  insure  the 
constant  stirring  of  the  mixture,  on  account  of  the  weight  of  the 
Paris  green,  which  causes  it  to  settle  very  rapidly.  Without 
care  in  this  regard  one  will  be  applying  at  one  time  almost 
pure  water,  and,  at  another,  two  or  three  times  the  proper 
strength  of  Paris  green.  Not  only  is  such  carelessness  likely 
to  result  in  injury  to  the  tree,  but  will  greatly  diminish  the 
effectiveness  of  an  application. 

Differences  in  Location. — The  fact  is  not  generally  appre- 
ciated that  the  habits  of  the  moth  are  very  different  in  different 
localities,  so  that  the  plan  of  procedure,  especially  the  time  and 
number  of  applications  necessary  for  effective  work,  will  vary 
in  different  regions.  There  are  a  few  regions  immediately 
adjoining  the  coast,  where  it  seems  possible  to  produce  apples 
with  but  little  codling-moth  injury  year  after  year,  without  any 
attempt  at  controlling  the  insect.  There  are  regions  in  which 
the  early  spring  application  (that  is,  the  one  that  is  applied  at 
blossoming  time)  can  be  dispensed  with  without  any  loss; 
again,  in  other  regions,  a  failure  to  attend  to  this  first  applica- 
tion will  conduce  to  a  very  great  loss.  Some  of  the  complaints 
made  against  Paris  green  have  been  due  to  a  failure  to  recog- 
nize these  differences  of  habit  in  different  locations,  and  the 
4ub 


—  30  — 

attempt  to  follow  blindly  the  practice  of  one  region  in  another, 
in  which  the  moth  shows  very  different  habits. 

Differences  of  Season. — There  seems  to  be  a  very  great  deal 
of  difference  in  the  habits  of  the  moth  from  year  to  year  in 
the  same  locality.  In  Berkeley,  for  instance,  while  during 
some  years  only  a  small  amount  of  injury  will  occur,  even 
with  no  spraying,  during  other  years  a  large  proportion  of  the 
fruit  will  be  wormy.  Some  of  the  complaints  against  Paris 
green  are  undoubtedly  due  to  the  fact  that  orchardists  have 
been  successful  with  one  line  of  procedure  during  one  season, 
and  have  followed  the  same  program  in  the  succeeding  sea- 
sons with  less  success.  The  proper  practice,  therefore,  in  any 
locality,  would  seem  to  be  the  one  which  would  insure  good 
results  in  the  season  most  favorable  to  the  moth,  even  though 
it  involve  a  little  extra  cost  on  the  other  seasons.  We  are  not 
yet  well  enough  acquainted  with  the  effect  of  the  character  of 
the  season  upon  insects  to  predict  the  result  with  much  cer- 
tainty; therefore,  it  would  be  well  always  to  be  on  the  safe  side. 

Importance  of  Treating  the  Codling-Moth. 

Where  apples  and  pears  are  grown  for  home  consumption 
simply,  and  where  the  codling-moth  is  not  excessively  abundant, 
it  may  be  all  right  to  neglect  treatment,  for  under  these  circum- 
stances the  fruit  is  usually  produced  in  superabundance  and 
the  presence  of  a  considerable  amount  of  wormy  fruit  is  not 
particularly  objected  to,  since  most  of  it  can  be  fairly  well 
utilized.  Whenever  these  fruits  are  grown  on  a  commercial 
scale,  however,  the  subject  becomes  a  much  more  important 
matter.  The  presence  of  any  considerable  quantity  of  codling- 
moth  will  seriously  decrease  the  quantity  yielded,  and  may 
make  all  the  difference  between  success  and  failure. 

Wormy  fruit  also  will  never  bring  on  the  market  a  price 
comparable  with  that  of  sound  fruit,  though  the  cost  of  grow- 
ing, picking,  packing,  and  shipment  is  the  same.  The  efforts 
made  by  the  fruit  inspectors  to  drive  wormy  fruit  from  the 
market  are  entirely  commendable,  and  it  will  be  but  a  very 
short  time  before  such  fruit  is  absolutely  unsalable.  No 
orchardist  can  afford  to  produce  any  large  amount  of  wormy 
fruit,  even  if  the  cost  of  treatment  were  equal  to  the  profits 
accruing  from  such  treatments.     With  proper  methods,  suffi- 


—  31  — 

cient  care,  and  persistence,  there  is  no  doubt  whatever  that 
the  injury  from  codling-moth  can  be  reduced  to  a  very  small 
percentage. 

The  Correct   Practices   for    Treating    the   Codling-Moth. 

No  simple  directions  can  be  given  for  the  destruction  of  the 
codling-moth,  which  will  be  applicable  in  all  fruit-growing 
regions.  The  correct  practice  in  this,  as  in  all  other  practices 
on  the  farm,  is  that  which  will  produce  the  maximum  profit  with 
the  minimum  expenditure. 

The  time  of  making  the  various  applications,  and  the  number 
of  applications,  and  the  need  or  uselessness  of  additional  pre- 
cautions, will  depend  upon  the  locality  and  can  only  be  learned 
by  a  study  of  local  experience,  and  by  practical  experiment 
by  the  orchardist.  There  are  some  general  principles  that  can 
be  laid  down  to  guide  in  the  proper  selection  of  methods  of 
treatment. 

Time  of  Application. — The  first  application  should  be 
made  in  most  localities  within  a  short  time  of  the  blossoming 
period.  In  those  places  and  with  those  varieties  in  which  all 
the  blossoms  open  out  about  the  same  time,  the  application 
should  be  made  as  the  last  of  the  petals  disappear.  When  the 
blossoming  is  slower,  so  that  some  fruit  will  begin  to  form 
before  the  last  is  out  of  the  bud,  it  may  be  necessary,  where 
the  codling-moth  is  bad,  to  make  an  application  in  the  midst 
of  the  blooming  season.  If  possible,  however,  the  tree  should 
not  be  sprayed  during  the  blooming,  as  the  blossoms  to  be 
fertilized  are  likely  to  be  killed,  or  prevented  from  setting 
fruit,  by  the  action  of  the  spray.  This  first  spraying  should 
be  made  in  almost  all  regions,  with  a  possible  exception 
of  the  immediate  coast,  where  there  is  some  evidence  that 
it  can  safely  be  omitted.  The  time  of  the  subsequent  applica- 
tions can  only  be  determined  by  careful  observation  in  the 
locality. 

Under  ordinary  circumstances  Paris  green  will  remain 
on  the  leaves,  sufficiently  strong  for  the  protection  of  the 
fruit,  for  three  or  four  weeks.  Under  favorable  circumstances 
it  may  remain  effective  even  longer  than  this;  and  on  the 
other  hand,  a  dashing  shower  of  rain  or  high  wind  may 
entirely  rid  the  trees  of  the  protection  afforded  by  the  spray; 


—  32  — 

they  should  be  then  at  once  re-sprayed.  There  is  danger 
to  the  tree  if  applications  are  made  too  often,  for  it  is  possible 
to  accumulate  the  poison  upon  the  leaves  by  repeated  spray- 
ings, so  as  to  seriously  injure  the  foliage.  For  late  fruit 
special  care  will  have  to  be  taken,  because  these  require  con- 
tinual spraying  until  late  in  the  season,  when  the  leaves,  being 
old,  are  particularly  susceptible  to  Paris-green  injury.  The 
great  abundance  of  codling-moths  at  that  time  of  the  year 
makes  the  complete  protection  of  the  fruit  imperative. 

Methods  of  Spraying. — In  spraying  for  the  codling-moth  the 
object  should  be  to  thoroughly  wet  every  part  of  the  plant,  for, 
as  we  know,  the  eggs  of  the  moth  are  left  indiscriminately  on 
the  leaves,  and  apparently  at  random,  by  the  moth;  and  the 
young  caterpillar  that  hatches  from  these  eggs  nibbles  here 
and  there  on  the  surface  of  the  leaves  or  fruit,  as  it  wanders 
about  in  search  of  a  hiding-place  where  it  may  begin  its  bur- 
rowing into  the  fruit.  This  hiding-place  is  almost  always  the 
blossom-end  in  the  case  of  young  apples  or  pears;  after  the  latter 
are  larger,  so  as  to  touch  each  other,  the  place  where  they  touch 
affords  a  very  satisfactory  hiding-place.  The  idea  should  be 
to  so  thoroughly  cover  the  plant  with  the  poison  that,  no  mat- 
ter where  the  caterpillar  may  attack,  its  first  meal  will  be  a 
poisonous  dose.  The  young  caterpillar  appears  particularly 
susceptible  to  poison,  so  that  it  is  desirable  that  the  first 
mouthful  should  be  partly  of  poison. 

Now  in  order  to  place  the  largest  amount  upon  the  plant,  it 
is  essential  to  spray  in  the  manner  that  will  leave  the  maxi- 
mum amount  of  water  upon  the  leaves  when  spraying  is  fin- 
ished; that  is,  to  cover  the  leaves  as  closely  as  possible  with 
the  dew-like  drops  produced  by  the  spray  nozzle.  If  the  leaf 
in  this  condition  is  shaken  these  globules  of  water  will  run 
together  and  part  of  it  will  drop  off  the  leaf;  or,  if  the  spraying 
is  continued  so  as  to  cause  them  to  run  together,  less  water  will 
actually  remain  on  the  leaf  than  was  there  before. 

In  spraying,  therefore,  it  should  be  the  intention  to  cover  the 
plant  very  uniformly,  using  only  enough  pressure  to  produce 
a  fine  mist;  or,  if  more  pressure  is  desired,  to  keep  the  nozzle 
far  enough  from  the  tree,  so  that  the  water  will  come  into  con- 
tact with  the  leaves  not  as  a  stream,  but  as  a  mist,  and  the 
moment  the  drops  begin  to  run  together,  so  as  to  cause  any 


—  33  — 

of  the  leaves  to  drip,  the  process  should  be  considered  com- 
plete. With  proper  spraying  there  should  be  scarcely  any 
water  on  the  ground,  but  practically  all  of  it  caught  and 
retained  by  the  leaves'.  This  brings  out  clearly  the  contrast 
between  the  kind  of  spraying  which  is  best  when  using  Paris 
green,  and  that  which  is  the  practice  with  the  washes  for  scale 
insects.  In  the  latter  case,  the  harder  the  stream  comes  in  con- 
tact with  the  plant,  and  more  free  the  use  of  the  spraying 
material,  the  more  likelihood  of  thorough,  satisfactory  work. 
Spraying  with  Paris  green  can  be  done  much  more  rapidly, 
and,  therefore,  much  more  cheaply  than  spraying  for  scale 
insects.  The  best  form  of  apparatus  to  be  used  will  depend  in 
part  upon  the  amount  of  work  to  be  done;  but  very  good  results 
can  be  obtained  with  a  small  and  cheap  outfit.  The  nozzle 
that  will  give  a  uniformly  fine  mist  should  be  selected.  There 
should  be  sufficient  hose  and  extension  rods  to  thoroughly  treat 
every  part  of  the  tree;  and  an  arrangement  to  insure  a 
thorough  stirring  of  the  Paris-green  mixture — more  thorough 
than  is  usually  provided  by  the  devices  for  automatic  stirring. 


EXAMINATION  OF  PARIS  GREEN  AND  SOME  OTHER 
ARSENICAL  SPRAYING  MATERIALS. 


By  Geo.  E.  Colby. 


The  enormous  increase  in  the  demand  for  Paris  green 
throughout  this  country  has  caused  manufacturers  to  put  upon 
the  market  materials  which  have  been  carelessly  or  hastily 
made.  It  is  not  an  uncommon  practice  to  use  needless  and 
excessive  amounts  of  arsenious  oxid  in  the  manufacture  of 
Paris  green;  or  the  finished  product  is  often  lower  in  this 
essential  than  is  lawful  in  the  State  where  made,  hence  this 
class  of  green  must  be  strengthened  by  the  addition  of  "  white 
arsenic"  (arsenious  oxid).  Thus  Paris  green,  which  at  best  is 
a  variable  compound,  comes  by  these  abuses  to  contain  free 
arsenious  oxid.  In  this  condition  this  substance  in  spraying 
materials  is  ready  and  certain  to  injure  and  destroy  foliage. 

The  application  of  compounds  carrying  any  soluble  leaf- 
destroying   matter    is    particularly    dangerous    in    semi-arid 


—  34  — 

climates.  From  experience,  horticulturists  have  learned  that 
arsenical  spraying  materials  are  often  unreliable  and  danger- 
ous, and  for  years  they  have  been  sending  samples  of  their 
purchases  of  Paris  green  to  this  Station'  for  examination  as  to 
purit}^.  The  greater  part  of  these  examinations  have  been 
made  with  the  aid  of  the  microscope  alone,  and  by  it  the  sample 
has  been  declared  fit  or  unfit  for  spraying  purposes.  This 
method  has  been,  fully  explained  in  the  first  part  of  this 
Bulletin  (see  page  13).  Lately,  within  the  last  few  months, 
manufacturers,  wholesale  druggists,  etc.,  have  seemed  to  realize 
that  their  goods  (insecticides)  will  always  be  condemned  by 
this  Department  if  they  show  impurity  upon  a  microscopic 
examination.  They  have,  however,  regarded  this  as  insufficient 
evidence.  Eastern  manufacturers,  therefore,  have,  through 
their  agents,  requested  this  Department  that  a  "  proper  analysis 
be  taken  "  of  their  goods;  meaning  thereby,  that  a  chemical 
analysis  be  made.  This  would,  according  to  their  understand- 
ing of  the  matter,  reveal  the  presence  of  a  sufficient  lawful 
quantity  of  arsenious  oxid.  At  the  same  time,  this  request 
indicates  an  awakening  interest  on  the  part  of  the  manufactur- 
ers and  dealers,  probably  because  they  want  information  which 
will  enable  them  to  make  their  output  of  insecticides — Paris 
green  in  particular — acceptable*  to  all.  It  is  to  satisfy  these 
requests  that  part  of  this  work  was  undertaken. 

Pure  Paris  Green,  also  called  Emerald  green,  Schweinfurt 
green  in  Europe,  is  an  aceto-arsenite  of  copper  and  may  be 
regarded  as  a  compound  of  verdigris  and  Scheele's  green  (arsenite 
of  copper),  having  this  percentage  composition:  Copper  oxid 
(CuO),  31.29;  Arsenious  oxid  (As203),  58.65;  Acetic  acid 
(C2H202),  10.06.  (Report  of  N.  J.  Agricultural  Experiment 
Station,  1897,  p.  408.) 

It  is  to  be  noted  that  Paris  green  usually  contains  very 
small  amounts  of  moisture  and  sulphuric  acid  (S03),  and  that 
the  arsenic  may  be  in  both  arsemc  and  arsenious  combination; 
also,  that  the  copper  may  exist  as  both  copper  oxid  (CuO)  and 
sub-oxid  of  copper  (Cu20).  But  one  essential  quality  of  pure 
Paris  green  is  that  it  is  wholly  insoluble  in  pure  water. 

Free  Arsenious  Acid  in  Unobjectionable  Samples  of  Paris 
Green. — An  1895  sample  of  green  pronounced  by  microscopic 
test  as  good  enough  for  spraying  purposes  showed  a  total  of 
54.10   per   cent   of   arsenious   oxid,  and  3.50  per  cent  of  free 


—  35  — 

arsenious  acid.  Another  good  green,  obtained  in  the  market 
in  San  Francisco  this  spring,  contained  4.1  per  cent  of  free 
arsenious  oxid. 

Analyses  of  Objectionable   Paris  Green   Containing   Free 
Arsenious  Oxid. 

The  following  analysis  of  a  sample  of  Paris  green  manu- 
factured in  New  York  City,  by  its  composition,  illustrates  quite 
fully  the  objectionable  ingredients  usually  found  in  one  class 
of  Paris  greens  which  this  Department  condemns  as  unfit  for 
spraying  purposes.  This  sample,  upon  a  microscopic  exami- 
nation, was  pronounced  unfit  for  spraying  trees  and  the  chemical 
analysis  more  than  justifies  the  conclusion. 

Analysis  of  Paris  Green  Manufactured  in  New  York  City. 

Per  Cent. 

Copper  oxid  (CuO) 31.25 

Arsenious  oxid  (As203),  combined __ 29.30 

Arsenious  oxid  (As203),  free 23.60 

Acetic  acid _ 11.28 

Sulphuric  acid  (S03) .23 

Water  (moisture) __ 1.31 

Silica .10 

Soda(Na20) .77 

Potash  (K20) trace. 

Lime(CaO) 10 

Zinc  oxid  (ZnO) _ _ 58 

Prussian  blue .75 

Total ..'. 99.27 

The  main  objection  to  this  sample  of  Paris  green  lies  in  the 
fact  that  nearly  one  quarter  (S3. 60  per  cent)  of  its  weight  is 
made  up  oifree  arsenious  oxid,  completely  soluble  in  hot  distilled 
water. 

Of  the  sum  total  of  the  other  ingredients  which  are  essen- 
tially impurities,  viz:  the  sulphuric  acid,  lime,  zinc,  and  the 
Prussian  blue,  only  the  last  named  compound  is,  by  its  pres- 
ence, at  all  significant.  This  material  is  commonly  used  as 
an  adulterant  of  verdigris,  and  while  the  amount  of  it  in  this 
Paris  green  is  small  (.75  per  cent),  it  seems  not  improbable 
that  it  was  used  to  give  a  greenish  tint  to  the  free  white  arsen- 
ious oxid. 

This  particular  case  shows  a  combination  of  materials  com- 
pounded and  sold  as  commercial  Paris  green  for  insecticide 


—  36  — 

purposes,  which  cannot  be  recommended  for  spraying  as  it 
stands;  its  sale  and  use  should  be  legally  stopped. 

Of  the  same  nature,  and  objectionable  for  the  same  reasons 
as  given  for  the  above  sample,  is  a  Paris  green  sent  here  by  the 
owner  of  a  large  orchard  who  u cleaned  the  leaves  off  his  trees" 
by  spraying  with  it.  This  material  contained  29.40  per  cent  of 
free  water-soluble  arsenious  oxid;  the  total  arsenious  oxid 
amounted  to  52.94  per  cent;  copper  oxid,  32.60  per  cent; 
besides  the  other  usual  components. 

Another  Paris  green  condemned  by  microscopic  test  was 
found  by  analysis  to  contain  24.60  per  cent  of  free  arsenious 
oxid;  total  arsenious  oxid,  55.13  per  cent;  copper  oxid,  26.70 
per  cent,  and  a  large  quantity  of  sulphate  of  soda.  The  makers 
of  this  material  claimed  that  it  contained  64.0  per  cent  of 
arsenious  acid  and  20  per  cent  of  copper  oxid,  and  seemed  to 
be  very  much  surprised  that  it  should  have  been  condemned 
by  the  microscopic  test. 

In  June,  1897,  a  sample  of  Paris  green  was  received  from  the 
Secretary  of  the  State  Board  of  Horticulture  of  California,  in 
which  the  microscope  showed  considerable  impurity  and  the 
sample  was  deemed  unfit  for  spraying — it  analyzed  as  follows: 

Per  Cent. 
Moisture 2.00 

Arsenious  oxid,  combined.- 42.27) 

Arsenious  oxid,  free  ._ 6. 70S 

Copper  oxid 27.93 

Sodium  sulphate 3.50 

Acetic  acid,  sand,  etc 17.60 

Total 100.00 

A  similar  green  to  the  one  just  recorded  came  from  San 
Francisco  in  March  of  this  year.  It  contained  impurities  by 
the  microscopic  test,  and  upon  analysis  showed  8.10  per  cent 
of  free  arsenious  oxid;  40.17  per  cent  of  combined  arsenious 
acid;  28.06  per  cent  of  copper  oxid;  2.31  per  cent  of  sulphate 
of  soda. 

A  remarkably  coarse-structured  Paris  green  with  very  large, 
heavy  crystals  and  much  impurity,  showed  by  analysis  to 
contain  9.10  per  cent  of  free  arsenious  acid;  39.58  per  cent  of 
combined  arsenious  acid;  34.60  per  cent  of  copper  oxid,  and 
1.50  per  cent  of  sulphate  of  soda;  acetic  acid  and  moisture, 
15.22  per  cent.     Of  course,  this  sample  was  condemned. 


—  37  — 

Aside  from  the  injurious  effects  upon  trees  from  the  use  of 
such  Paris  greens  as  described  above  there  is  another  aspect  of 
the  case,  viz :  the  fraud  connected  with  the  sale  of  such  mate- 
rials. For,  if  from  one  tenth  to  one  third  of  the  weight  of 
these  materials  is  made  up  of  free  "white  arsenic,"  worth  only- 
one  third  as  much  as  good  unobjectionable  Paris  green,  it  is 
not  difficult  to  see  where,  on  ton  lots,  the  manufacturer  makes 
large  unearned  gains. 

For  example,  if  a  wholesale  dealer  obtains  $240  a  ton  for  his 
article  and  if  it  contains  one  fourth  free  uncombined  arsenious 
oxid,  it  is  a  simple  matter  to  see  that  he  has  an  unearned  gain 
of  about  17  per  cent.  By  the  time  the  consumer  has  his  small 
lot  of  such  objectionable  Paris  green  at  25  and  30  cents  a  pound, 
it  becomes  a  very  expensive  material  for  his  purpose. 

Fortunately  for  the  farmer,  the  remedy  for  all  this  is  prac- 
tically in  his  own  hands,  as  pointed  out  in  the  first  part  of  this 
Bulletin.  He  has  only  to  procure  two  cheap  materials — "white 
arsenic"  and  lime — and  by  simple  processes  combine  them  into 
an  insoluble  arsenite  of  lime— -an  inexpensive,  effective  insecti- 
cide, which  will  not  injure  his  orchard. 

Adulteration  of  Paris  Green. 

This  Station  has  never  yet  analyzed  a  sample  of  Paris  green 
in  which  adulterants  were  added  to  the  extent  reported  of 
foreign  paint  materials. 

This  is  also  the  experience  of  several  Eastern  experiment 
stations.  In  Germany  the  case  is  quite  different,  for  much 
adulterated  green  is  found  containing  barium  sulphate,  calcium 
carbonate,  chrome  yellow,  iron  oxid,  lead  chromate,  etc.  In 
part  these  materials  are  simple  make-weights,  while  others  are 
added  in  order  to  produce  different  desired  tints  of  color. 

Examination  of  Some  of  the  Newer  Substitutes  for  Paris 

Gr^en. 

"ARbENOIDS." 

During   the   last  year  several  samples  of  what  are  called 

"arsenoids"  and  described  as  white,  or  barium  arsenite,  pink, 

or  lead  arsenite,  and  green,  or  copper  arsenite,  by  their  maker, 

have  been  received  for  experimental  purposes  at  this  Station. 

5ub 


—  38  — 

si  White  Arsenoid"  or  Barium  Arsenite. — This  material  upon 
analysis  was  found  to  be  of  the  following  composition: 

Per  Cent. 

Barium  carbonate 44.05 

Barium  chlorid _ 13.05 

Barium  oxid _ 8.18 

Arsenious  oxid,  free 27.64 

Lead  carbonate _ ._ 1.86 

Silica... >. 20 

Moisture ._ _ 4.00 

Total 98.98 

The  only  ingredient  which  might  give  this  compound  a  value 
for  spraying  trees  is  the  arsenious  oxid.  But  all  of  this  oxid  is 
in  such  a  condition  that  it  is  extremely  dangerous  to  foliage, 
and  practical  tests  have  shown  it  to  be  so.  Of  the  other  com- 
ponents, the  largest,  barium  carbonate,  simply  makes  weight 
and  adds  nothing  to  its  value.  The  same  is  true  of  all  the 
other  ingredients.  Notwithstanding  that  this  material  is 
offered  for  a  much  lower  price  than  Paris  green,  it  can  not  be 
safely  recommended. 

"  Pink  Arsenoid,"  or  Lead  Arsenite. — This  material  is  lead 
arsenite,  colored  with  some  pink-colored  aniline  residue,  and 
shows  the  following  composition  by  analysis: 

Per  Cent. 

Lead  oxid  (PbO)... 49.58 

Arsenious  oxid  (As203),  combined 40.02 

Arsenious  oxid  (As203),  free 3.24 

Moisture _ 31 

Organic  matter  from  aniline  residue;  lead  sulphate,  etc...      6.85 

Total 100.00 

This  compound  cannot  be  objected  to,  and  a  practical  test 
with  it  shows  that  it  is  perhaps  but  little,  if  any,  more  danger- 
ous to  foliage  than  Paris  green.  It  is  sold  for  much  less  than 
ordinary  green;  this,  when  considered  with  the  low  content  of 
free  arsenious  oxid,  should  recommend  it. 

"  Green  Arsenoid,v  or  Copper  Arsenite. — This  compound  is 
"dead"  green  in  color,  and  under  the  microscope  is  seen  to  be  a 


—  39  — 

mass  of  irregular,  sharp  crystals.  It  shows  the  presence  of 
some  soluble  blue,*  which  often  contains  arsenic.  It  analyzes 
as  follows : 

Per  Cent. 

Copper  oxid  (CuO) 28.83 

Arsenious  oxid  (As203),  combined 53.51)    ^  ^ 

Arsenious  oxid  (As203),  free 7.82) 

Moisture - 2.77 

Silica _ ._. 40 

Organic  matter   derived    from  soluble  blue;  sulphate  of 

soda,  etc 6.67 

Total 100.00 

While  this  material  contains  the  guaranteed  quantity  of 
arsenious  oxid,  and  is  cheaper  than  the  common  green,  still  it  is 
hardly  safe,  as  it  stands,  to  use  in  this  climate  with  its  nearly 
eight  per  cent  of  free  arsenious  oxid. 

It  appears  from  the  foregoing  record  that  of  these  "arsen- 
oids"  the  lead  compound  is  the  best;  i.  e.,  the  least  injurious. 
The  copper  compound  is  certainly  promising,  and  if  proper 
methods  are  followed  in  its  manufacture  it  can  easily  be  made 
a  desirable  insecticide.  But  of  the  barium  compound  nothing 
more  need  be  said  than  that  it  is  simply  worthless.  It  is  a 
grave  mistake  to  put  it  on  any  market  for  the  use  for  which 
it  was  intended. 

PARAGRENE. 

Another  of  the  newer  arsenical  spraying  materials  is  a 
patented  article  bearing  the  name  "Paragrene."  A  sample  of 
it  has  very  lately  been  received  for  examination  by  this  Sta- 
tion. The  manufacturers  of  paragrene  claim  "  that  the  article 
was  very  extensively  used  last  year  by  planters  and  growers 
all  over  the  country,  and  that  it  is  free  from  the  objectionable 
features  of  Paris  green,  as  it  does  not  burn  or  scorch  the  most 
tender  foliage.  It  contains  the  required  percentage  of  arsenic 
or  any  arsenious  oxid.  Besides  this  the  article  is  considerably 
cheaper  than  Paris  green."  It  retails  at  from  13  to  17  as 
against  25  or  30  cents  per  pound  for  Paris  green. 

A  microscopic  examination  shows  that  this  sample  contains 
besides  the  ordinary  green  a  considerable  quantity  of  sulphate  of 
calcium  (gypsum)  and  also  many  crystals  of  " white  arsenic." 

The  substance  analyzed  as  follows: 

*  Sodium  triphenylrosaniline-monosulphonate. 


—  40  — 

Per  Cent. 

Copper  oxid  (CuO) 23.46 

Arsenious  oxid  (As203),  combined 17.52 

Arsenious  oxid  (As203),  free.. ._ 23.08 

Acetic  acid __.     6.72 

Calcium  sulphate  (gypsum) _ 19.31 

Sodium  sulphate 2.26 

Sodium  chlorid _ 25 

Peroxidof  iron 20 

Water ..- _ 6.20 

Total 99.00 

Notwithstanding  that  the  above  composition  complies  in 
many  particulars  with  the  claim  made  for  it  in  the  Patent 
Office,  the  fact  that  it  contains  so  much  (nearly  one  fourth  its 
weight)  of  free,  water-soluble  arsenious  oxid  stands  against  it. 
In  this  sample  of  paragrene  the  free  arsenious  oxid  rates  the 
same  as  in  some  of  the  most  objectionable  Paris  greens.  This 
article,  therefore,  must  be  rejected,  as  it  will  positively  cause 
injury  to  foliage  if  used  in  California  orchards. 

Summary. 

The  results  of  this  examination  of  Paris  green  and  other 
arsenical  spraying  materials  may  be  summarized  as  follows: 

First — That  many  Paris  greens  nowadays  contain  large 
amounts  of  free  water-soluble  arsenious  oxid,  the  manufacture 
and  sale  of  which  should  be  discontinued,  both  because  these 
materials  have  proven  injurious  and  unsatisfactory  in  horti- 
cultural work,  and  because  they  constitute  a  very  obscure  form 
of  fraud  upon  the  purchaser. 

Second — That  the  microscopic  examination  of  a  Paris  green 
affords  sufficient  evidence  for  rejecting  it  if  it  contains  as  much 
as  6  per  cent  of  free  arsenious  oxid;  and  above  this  figure  there 
is  no  question  of  the  great  value  of  this  rapid  and  excellent  test. 

Third — That  adulteration  in  the  sense  of  added  foreign 
matter  to  Paris  green  (e.  g.,  barium  carbonate,  calcium  car- 
bonate and  sulphate),  is  rarely  practiced  in  this  country,  at 
least  by  the  manufacturers. 

Fourth — That  the  newer  spraying  materials,  from  the  evi- 
dence at  hand,  with  the  exception  of  the  very  injurious  barium 
compound  and  the  paragrene,  will  doubtless  prove  acceptable 
and  cheap  substitutes  for  Paris  green,  if  the  quantity  of  free 
arsenious  oxid,  especially  in  the  green  one,  is  better  governed  by 
proper  methods  of  manufacture. 

c 


